This doesn't affect your filed tax return since the rollover is still nontaxable. What does change is the amount of contribution basis that TurboTax recorded on the IRA Information Worksheet as the amount of basis acquired from the Roth TSP. You can correct this by amending in TurboTax, but just not sending the amendment to the IRS.
The alternative is to not bother changing it in 2023 TurboTax and just make the correction to your basis in 2024 TurboTax after transferring your 2023 tax file in to start your 2024 tax return, but that will require that you remember to make the correction next year when preparing your 2024 tax return.
