Pension State and Federal Withholding

I receive a pension and a 1099-R for it. Initially, nothing was being withheld for state or federal - I changed it to have a state and federal witholding. Turbotax is asking if the taxable distribution for the state is different from the federal. My box 16 is blank - so should I enter the box2a as a subtraction? Perhaps my pension is not taxable in the state of california?