Assuming we're talking about long term losses, look for your "California Capital Loss Carryover Worksheet" for 2017. Line 8 (Part I, assuming you're a CA resident) should have the amount to carryover to 2018.
You ought to be able to find the same line on the same worksheet for 2016, to see if there's a difference.
I always generate and save a PDF of the "for filing" and "for records" returns upon completing my taxes each year. That makes it easier to go back and check previous returns...
