What number should I enter in "How much of the federal W-2 did you earn in California?

you got 2 w-2s. the state, state wages atate wages can be more then federal

box 12 w is for contributions to HSA 

you enter the w-2 info just as shown but in your situation, you have 2 W-2s to enter. CA does not allow a deduction for HSA contributions. So box 16 is bigger by the HSA contribution.

Your W-2's should have the wages earned in each state broken out for you in Box 16.  Use that amount for State Wages to report. 

The Code W in Box 12 of your W-2 indicates company contributions to an HSA, so that is not included in your Box 1 Wages on your Federal return.

Here's more info on Reporting HSA Contributions.