No error. Turbotax is doing the calculation correctly
my tax handbook says the following for line 1 of the ROTH contribution worksheet
enter MAGi. footnote says to subtract income from ROTH conversion from MAGI
PUB 590A Roth worksheet
1) Enter your adjusted gross income from Form 1040, 1040-SR, or 1040-NR,
2 ) Enter any income resulting from the conversion of an IRA (other than a Roth IRA) to a Roth IRA (included on Form 1040, 1040-SR, or 1040-NR, line 4b) and a rollover from a qualified retirement plan to a Roth IRA (included on Form 1040, 1040-SR, or 1040-NR, line 5b).
3) Subtract line 2 from line 1
