Not everyone stops working at 60, and what you want to happen is for the calculator to accommodate that fact, because those extra years worked in one's sixties may turn out to be among the highest 35 years of earnings. If you put in the year she turns 62, what that calculator shows is that, in calculating the AIME, wages are indexed by the national average wage index until she turns 60. After she turns 60, if she is still working, any wages earned are not indexed. That is why the last two years' indexing factors are 1.0000 They represent wages earned the year she turns 60 (you never inflation adjust the current year) and the year she turns 61, which are not indexed.
You have said that your wife won't turn 60 until 2023. If we wanted to be completely accurate, you would put 2025 into the calculator, since that is the year she turns 62. But the calculator cannot currently run that calculation (try inputting 2025 - it doesn't work), because it does not know what the national wage index will do for the years of 2022 and 2023. My suggestion of putting 2023 in the box is just a way to get some rough idea of the indexing factors. They will be higher than the calculator shows, because she still has two more years of indexing left (if you put 2023 in the box, it only shows indexing through 2021). I apologize for not being clearer about that.
To repeat what I said earlier, at this point you can only estimate. You won't know her benefit for certain until she applies and the SSA calculates it. If you underestimate, that can only be to your benefit when the money actually starts coming in.