State mandatory taxes generally flows from box 14 of your Form W2.  It sounds like there might be a decimal point out of place and you should review those entries.  Also, it shows you are using the desktop program.  You can switch to the Forms Mode and check for the State and Local Tax Deduction Worksheet (line 17) to see if that number appears there also.  

Also, state mandatory taxes are deductible taxes that are imposed on you by the state that are not direct income taxes (such as unemployment or disability insurance payments that go to the state).

In some states Disability Insurance is mandatory. In California it is the total of CA SDI paid in all your W-2 Box 14s.

Thank you SO much! This is exactly what happened. Turbo Tax auto-filled this number, missing the decimal point! BUT I still can't figure out how to FIX it. Can you say more about how to do that?

Update: I figured out how to fix it! I had to go back in to Wages & Income, review the Wages & Salary pieces.  

Is this a new thing? I don't believe in prior years that Turbotax would include the CASDI payment for Schedule A line 5a.

Yes, TurboTax included the CASDI payments in the past, but only if they were included in the Box 14 of the W2. 

@Skyxliner

Ahh Thanks Mary! @MaryK4 

I double checked prior years and that's how it was calculated as well. My mistake.

The only way I knew is that there was a return with "extra" state tax deduction on the Schedule A so I looked for it.  Thanks for asking- that's why we are here!

@Skyxliner

would be nice if Mr. Turbo could add that  explanation on the software

In previous years, my "State and Local taxes greater than 10K" was zero.  In 2021, it's around -20K, which takes a huge chunk out of my itemized deduction total.  Our salaries are about the same.  I assume this is because of SALT laws.  But I thought that passed in 2017.  And my SALT over 10K line was zero until year 2021.  Does anyone know why that is?