OK ... so they changed the amount of the stimulus credit which cascaded down the rest of the form. The program asks you to enter the amount of stimulus payments you got in advance so if you entered the wrong amount this was not a TT error and is not covered by the accuracy guarantee.
Now if you disagree with the IRS's position on how much stimulus money you got in advance you need to have a trace put on the check(s) ...
Maybe it went to an account you don't remember. Or you got a check or a card. It was probably easy to miss the debit card in the mail and think it was junk mail. They have to put a trace on it.
How to put a trace on a missing 1st or 2nd Stimulus payment. IRS for Payment Issued but Lost, Stolen, Destroyed or Not Received
See question F3 here, you can expand it to see how to put a trace on it.
https://www.irs.gov/newsroom/2020-recovery-rebate-credit-topic-f-finding-the-first-and-second-econom...
