California Code, Elections Code - ELEC § 9310

(a) If the initiative petition is signed by voters not less in number than 10 percent of the voters in the district, if the total number of registered voters is less than 500,000, or not less in number than 5 percent of the voters in the district, if the total number of registered voters is 500,000 or more, the district board shall do either of the following:

(b) The number of registered voters referred to in subdivision (a) shall be calculated as of the time of the last report of registration by the county elections official to the Secretary of State made before publication or posting of the notice of intention to circulate the initiative petition.