I contributed/converted to both tax year 2019 and tax year 2020 in year 2020 and got two 1099R forms. How do I enter them in tt to generate correct 8606?

I tried following https://thefinancebuff.com/how-to-report-backdoor-roth-in-turbotax.html but it only works for current year. When I add the other 1099R(for 2019) it starts to reduce my refund amount.