As long as you did not have a distribution in 2018 then that is a quirk in TurboTax. Line 4 will be blank, but if there is a distribution that files out lines 6-15 then line 4 WILL populate. It is a small bug that makes no difference.
It appears that you found the issue with the 2019 contribution that should not have been on line 4 unless you made it in 2020.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
