1099-R Box 7 Code G

In 2020 I made an in-plan conversion within my 401k,  from traditional non-Roth to Roth. This was the first time I made such conversion.

On the 1099-R,  boxes 1, 2a, and 16 showed the amount converted; box 7 was coded G and IRA/SEP/Simple box was not checked. All the other boxes were either blank or not checked.

I understand the converted amount was counted as taxable income. But when I entered G in box 7, Turbo Tax showed no tax on the amount converted.

Did I do anything wrong or any bug in the software?

Thanks for your help!