Line 29 is for excess casualty loss, and has nothing to do with depreciation.
Line 41 is the depreciation percentage, not the dollar amount.
There's an IRS Form 4562 that prints in landscape format, specifically titled "Depreciation and Amortization Report'. On that form add together the amounts in the "prior year depr" column and "current year depr" column, to get the total amount of depreciation taken on the property, up to and including 2020 depreciation.
Thanks Carl!
My mistake: I had looked at the line numbers on an old Form 8829 (2017 version), and the numbers have changed. I should have referred to lines 30 and 42 (instead of lines 29 and 41) in my question.
Are these the right numbers to look at for previous years?
Don't go by the 8829, as it may not be for "that" specific property only. Use the IRS Form 4562 for that specific property. There are two form 4562's for each rental or royalty activity. Both of them print in landscape format and have different titles. You want the one titled "Depreciation and Amortization Report".
To see them, you usually have to elect to save your return in PDF format to your computer. Elect to save "EVERYTHING", and not just the "forms required for filing" or the "forms for your records". Then you'll find the 4562 you need, in that PDF file and if needed, you can print just that page.