Why does california PTE tax payment reduce california income to calculate PTE?

CALIFORNIA TAXABLE INCOME IS $$140,000$

Next year CA charitable contribution: $$10,000.$

PTE CALCULATED ON TAX SOFTWARE IS : $12,090(140,000-10,000)$x$9\mathrm{.}3\%$

Why isnt the CA PTE TAX $13,020(140,000$x$9\mathrm{.}3\%)$