I'm a fellow user and can't speak much specifically about California's 540 Schedule CA (Adjustments), but many states have such adjustment forms. The state taxable income is not always the same as the Federal amount. The adjustment schedule is used to adjust the Federal AGI and some Federal deductions on the California return according to California law. Some people will have "additions and subtractions" they can make to the Federal figures on the state return, which may increase or lower their taxable CA income, thus affecting their state refund or state tax due.
The 540 Schedule CA (or 540NR Schedule CA, etc.) instructions and viewable forms should normally be on the CA state tax website. The specific ones would depend on whether you are are a resident of CA, non-resident, or part-year resident. However, it looks like the 2019 form is not yet available on the CA website. If you want to see what one looks like, it does let me pull up the 2018 Schedule CA and instructions there.
https://www.ftb.ca.gov/forms/index.html
