The reason this happened was because I used one of the early releases of TurboxTax 2020 to estimate my taxes for 2020. I recall that I entered $2400 ($1200x2) into the form manually as I did not see a step-by-step question about it (it may have been there and I didn't find it). When Congress authorized the additional $600 per person, TurboTax updated the software. After I updated the software I opened my file again and did find the step-by-step question and answered it (stating that we did not receive any stimulus money during the year). After I did that, the number in the form should have been $3600 (($1200+$600)x2) but instead it showed $4800. I called support and asked about this, the solution we found was to manually enter the correct numbers in the form. The TurboTax support line did not have much of an explanation on why this happened, although they did claim that an important recent Windows 10 update had not been done on my computer. I personally think it was a bug in the TurboTax software.
