Cal. Sts. & High. Code § 19167

Upon the presentation of a petition pursuant to this chapter, the clerk of the board of supervisors shall immediately refer the same to an appropriate county officer, who shall certify to the board the number of owners of taxable property within the boundaries of the district or the proposed zone whose names appear on said petition, together with the percentage of the total assessed valuation of all taxable property within the boundaries of the district or zone, which said signatures represent.