Thank you, all! I now realize the discrepancy was that I used the FMV at the time because it was lower than the purchase price (as TT obviously instructed me to do). Also, land/home was allocated properly (taken from the property tax statement).
So my thinking now is that my depreciation has been correct all along and no adjustment is actually necessary.
Regarding the sale of the property and reporting it on my 2020 return, I believe I would use the purchase price when reporting the disposal of this asset to calculate any gains, right? After the depreciation, there is a very small gain that I will have to pay taxes on and I am withholding that amount for CA on form 593. I will also make an estimated payment via 1040ES for the Fed. I'm hoping it shouldn't matter that the depreciation schedule used a lower amount than what the actual purchase price was since that was the correct way to do it. My main concern was that the amount on the depreciation schedule was less than the purchase price and for the life of me I could not figure out why I would have done that 10 years ago (until reading your responses). Phew.
