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The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":700,"source":{"system":"sec-edgar","filing":"0002070849-26-000067","document":"wk-form4_1789083874.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":17,"url":"https://www.sec.gov/Archives/edgar/data/2070849/000207084926000067/wk-form4_1789083874.xml","form_type":"4"}},{"id":4615373,"issuer":{"id":3992,"kind":"organization","name":"BillionToOne, Inc.","symbol":"BLLN"},"owners":[{"id":73350,"kind":"person","name":"Lynch Thomas P.","position":1,"cik":"0001659824","reported_name":"Lynch Thomas P.","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"See Remarks"}}],"security":"Class A Common Stock","published_at":"2026-09-10T23:44:37.000Z","date":"2026-09-08","kind":"sale","planned":true,"acquired":false,"shares":2518,"price":100.1959,"value":252293.2762,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 8, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F10","text":"The reported price in Column 4 is a weighted average price. 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These shares were sold in multiple transactions at prices ranging from $98.340 to $99.230 per share, inclusive. 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The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":4173,"source":{"system":"sec-edgar","filing":"0002070849-26-000067","document":"wk-form4_1789083874.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":13,"url":"https://www.sec.gov/Archives/edgar/data/2070849/000207084926000067/wk-form4_1789083874.xml","form_type":"4"}},{"id":4615369,"issuer":{"id":3992,"kind":"organization","name":"BillionToOne, Inc.","symbol":"BLLN"},"owners":[{"id":73350,"kind":"person","name":"Lynch Thomas P.","position":1,"cik":"0001659824","reported_name":"Lynch Thomas P.","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"See Remarks"}}],"security":"Class A Common Stock","published_at":"2026-09-10T23:44:37.000Z","date":"2026-09-08","kind":"sale","planned":true,"acquired":false,"shares":385,"price":99.223,"value":38200.855,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 8, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F7","text":"The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.830 to $99.825 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":5304,"source":{"system":"sec-edgar","filing":"0002070849-26-000067","document":"wk-form4_1789083874.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":12,"url":"https://www.sec.gov/Archives/edgar/data/2070849/000207084926000067/wk-form4_1789083874.xml","form_type":"4"}},{"id":4615368,"issuer":{"id":3992,"kind":"organization","name":"BillionToOne, Inc.","symbol":"BLLN"},"owners":[{"id":73350,"kind":"person","name":"Lynch Thomas P.","position":1,"cik":"0001659824","reported_name":"Lynch Thomas P.","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"See Remarks"}}],"security":"Class A Common Stock","published_at":"2026-09-10T23:44:37.000Z","date":"2026-09-08","kind":"sale","planned":true,"acquired":false,"shares":358,"price":100.8234,"value":36094.7772,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 8, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F6","text":"The reported price in Column 4 is a weighted average price. 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The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote."}],"balance_after":5689,"source":{"system":"sec-edgar","filing":"0002070849-26-000067","document":"wk-form4_1789083874.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":11,"url":"https://www.sec.gov/Archives/edgar/data/2070849/000207084926000067/wk-form4_1789083874.xml","form_type":"4"}},{"id":4615367,"issuer":{"id":3992,"kind":"organization","name":"BillionToOne, Inc.","symbol":"BLLN"},"owners":[{"id":73350,"kind":"person","name":"Lynch Thomas P.","position":1,"cik":"0001659824","reported_name":"Lynch Thomas P.","relationship":{"director":false,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"See Remarks"}}],"security":"Class A Common Stock","published_at":"2026-09-10T23:44:37.000Z","date":"2026-09-08","kind":"sale","planned":true,"acquired":false,"shares":2997,"price":100.1135,"value":300040.1595,"ownership":{"direct":true},"footnotes":[{"field":"kind","element":"transactionCoding","label":"F1","text":"The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 8, 2026."},{"field":"price","element":"transactionPricePerShare","label":"F3","text":"The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.585 to $100.565 per share, inclusive. 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