Cal. Elec. Code § 7650
In each county containing less than five Assembly districts or portions thereof, except the City and County of San Francisco, a county central committee of at least 25 members shall be elected by supervisor districts, and the number elected from each supervisor district shall be determined as follows:
The number of voters registered as members of the American Independent Party, as reflected in the statement of voters and their political affiliations transmitted to the Secretary of State on or before the 135th day before any primary election, shall be divided by 25. The number thus derived shall be divided into the number of American Independent Party voters registered in each supervisor district, and the integer nearest the resulting quotient shall be the number of central committee members to be elected to represent that supervisor district.
Ca. Elec. Code § 7650