Roth IRA conversion: taxable or nontaxable

Hi, I am doing my 2024 tax return. The system is asking me to confirm net conversions to my Roth IRA that were taxable and nontaxable in 2021.

Basically, I deposited 6000*2 into my traditional IRA account between Jan-April 2021, using the quote of both tax year 2020 and 2021. Then I converted $12000 to Roth IRA in 2021.

I did the same thing for 2022 and 2024. I deposited 6000+6500 into my traditional IRA account between Jan-April 2023, using the quote of both tax year 2022 and 2023. Then I converted $12500 to Roth IRA in 2023.

However, after reading my tax 2023 return info, turbo tax automatically put my 2021 conversion of $12000 as taxable, and 2023 conversion of $12000 as non taxable. It makes me very confused. One of it must be wrong.

Are these conversion taxable or nontaxable? Does error result from any error from my 2023 return? What's the impact of the error? Anything I should do to correct my previous return?