@ZachPro some ideas on where to look:
did you use Turbo Tax to complete your 2021 tax return?
If you used Turbo tax do you remember right clicking and overriding any of the fields? that is a "no-no" as it invalidates the turbo tax guarentee; also frequently you can't efile the tax return
if Line 15 is $78,751, then line 16 should be $13,079. it is right from the table on page 74.
https://www.irs.gov/pub/irs-prior/i1040gi--2021.pdf
are you confident you are posting the correct line numbers? were you self-employed and that tax number is really Line 24, which would include the Self Employment tax?
the link you posted above is the 2022 tax instructions yet you state that you were reviewing your 2021 tax return. Which year are we really dealing with? (and that is why you state the table says $12,948 and I say $13,079 - because there are two different years being discussed.
