Why is my entire 2020 UI being applied to my 2020 AGI when I repaid several thousand dollars for prior years? Shouldn't that repayment come off the top?

I received roughly $12k in unemployment benefits for 2020 (none of the COVID benefits had their taxes withheld). I repaid roughly $3-4k of that before even seeing it for tax year 2017. Shouldn't my UI be $8-9k for AGI? (rough numbers due to incorrect 1099-G received; waiting on corrected)