How do I find the depreciation schedule that was used in my previous years' taxes?

In last year's printout look for the two form 4562's that print in landscape format. One is title "Depreciation and Amortization Report" and is the one more commonly used. The other is title "Alternative Minimum Tax Depreciation Report" and is only used if AMT applies to you in a given tax year.

The form will show you the current year's depreciation taken, the total of all prior year's depreciation taken, business use percentage of the asset(s), date placed in service, depreciation method/convention, and any SEC 179 or SDA allowances taken on any assets.

For "the math" used by the program, see IRS Publication 946, How to Depreciate Property, at https://www.irs.gov/pub/irs-pdf/p946.pdf