If you entered all your itemized deductions and your federal standard deduction is still bigger that itemized deduction, you can use the standard deduction plus deduct up to $300 for cash donations made to qualifying charities this year.

The CA return will use all of your itemized deductions entered in your Federal return if the total amount of itemized deductions exceed the CA standard deduction. 

You don’t get both the special $300 deduction for charitable donations for people who claim the standard deduction and also get to  itemize your deductions.  You should enter all of your itemize deductions in the program and let the program do what is correct for your overall situation.