Traditional IRA conversion to Roth IRA tax treatment

In 2019 I converted a traditional IRA to a Roth IRA. The 1099-R shows the gross distribution as $18,831 and taxable amount is the same, both boxes in 2b are checked, and the box 7 distribution code is 2. However, the traditional IRA had a basis of $18,000, because all of my contributions were non-deductible. PROBLEM: After entering all this info in TurboTax, it is including $17,995 of the $18,831 in my income. That's like taxing me twice on the non-deductible contributions, isn't it? It's making the tax due too high. I've been through the related interview sections and the tax forms view in TurboTax and still can't figure what is causing this.  Am I missing something or is TurboTax not calculating this correctly?