I think I might have misunderstood what you did because the details you provided are perhaps incomplete. I interpreted the question as indicating that you entered the wrong amount when TurboTax asked how much of your distribution was RMD, not that you entered a different amount in any of TurboTax's 1099-R form boxes than the amounts actually shown on any Forms 1099-R provided by the payer.
Where did you put the wrong amount when you completed your 2019 tax return? You should have entered the details on any Forms 1099-R exactly as received. If you modified any of the amounts (generally box 1 or box 2a), it's likely that you filed an inaccurate tax return.
Which year's RMD was taken late in January, 2019? In which year did you receive this distribution, 2020? Was the "late" RMD that you took in January an RMD for the first year you were required to take an RMD from this account? Does your 2019 Form 5329 show $0 on lines 54 and 55, with the notation "RC" and the amount of your late RMD next to line 54?
