Nevermind - the issue was on the "Let's enter <Person>'s HSA contributions" page.
It already listed how much the combined contribution was and I added another $4900 in the box below. I was so used to see "this is what you did in 2020, now enter what you did in 2021" that I thought that other $4900 was from 2020 and not what it already knew about 2021.
My bad.
