California Code, Elections Code - ELEC § 13217

(a) The number on each ballot shall be the same as that on the corresponding stub, and the ballots and stubs shall be numbered consecutively in each county, or the ballots and stubs may be numbered consecutively within each combination of congressional, senatorial, and Assembly districts in each county.  In a partisan primary election, the sequence of numbers on the official ballots and stubs for each party within each county, or within each political subdivision in each county, shall begin with the number 1.

(b) In counties using vote centers, ballots may be serialized in the way that best promotes ballot accounting and with the greatest economic efficiency for the county.