Retirement tax questions

It looks like we are halfway there.   Specifically, my 1099-r shows the $6k conversion for 2019 and $6k conversion for 2020 (i.e. $12k total).  Once that form is entered, my federal tax goes up and it appears TurboTax online thinks I have tax due, presumably for the 2019 conversion.  Since IRA contributions for 2019 were possible all the way to July 2020 (I did mine in May 2020), then the resulting 1099-r could have backdoors for two possible years (i.e. my 2020 1099-r has data for my backdoor activity for 2019 *and* 2020).  How do I enter this?