@SuburbanMom – did you by any chance pay a large amount in state income taxes, perhaps disproportionate to your income? I’m a little fuzzy on the details because it was a long time ago, but the year before the tax year that counted for FAFSA, I had a large capital gain due to the sale of family owned property that I had inherited a share in. So I had to pay a big chunk of money in taxes. So the next year when I filed – the tax year that counted for FAFSA - I took a deduction for all of those state taxes on my schedule A (itemized deductions) – as I should have.
My daughter’s college also did something similar, changed the FAFSA probably by making the change on the taxes paid line I contacted them and they explained what they had done and why. Basically they saw I had paid a whole bunch of taxes and they were giving me credit for it, but there isn’t an “other” line on the FAFSA, so they made corrections to the nearest thing.
Anyway, it sounds like something similar may have happened in your case.