Deductions & credits

We did take mileage deduction over depreciation method. So I don’t understand why it’s asking for depreciation values of mileage for prior years ( not 2021) in category for business portion expense for mileage depreciation ( states to multiply rate given by number miles deducted in 2020) and the ask for AMT business  portion expense for prior year  . This screen is not understood cause in end is showing a gain. This was simply a vehicle that we bought personally in 2019 that in 2020 August began using as personal and business and continued to use for personal and business in 2021 until traded in on 7/2021