Spouse Traditional IRA Contribution

Hi, my spouse and I are filing jointly this year. I have earned income and my spouse does not. Both of us contributed $6000 each to traditional IRA and then converted to Roth IRA (total we contributed $12000).

 

Since my income exceeds the limit for tax-deduction, all of our contributions are not tax-deductible. I am assuming all of the $12000 contributions are not taxable as well since we are using post-tax dollars to contribute. However, the turbo tax shows that $6000 out of $12000 contribution is taxable.

 

Can someone help me navigate this issue? Thanks a lot.