This is a situation where I would amend the return and remove the $20,400 in unemployment so TurboTax does not give you a refund again.
The whole credit is an unique situation that does not fit the mold of any other year's amendment. Someone may post a better answer.
if you are using TurboTax Online you can't do that. This is a serious flaw in TurboTax Online.
You need to contact Customer Support and get them to give you a download of desktop program, so you can get to the forms.
You can go to the line where you report unemployment and manually subtract $20,400 from the unemployment received and change the number to the remainder of that equation.
For example, if you received $30,000 in unemployment, you can change your unemployment received to show just $9,600. You do not need to access the forms to make that change.
That might trigger a review by the IRS, but your figures will be correct on the amend.