SCENARIO: I have a vehicle that was purchased new and put into service in 2010 for our small business. The vehicle was used for business less than 100% of each year (less than 50% some years). Each year, the standard mileage rate was applied. The vehicle was then sold in 2019.

QUESTION: In order to determine the depreciation equivalent, do I (1) calculate the 'Rate of Depreciation Allowed in Standard Mileage Rate' for each of the ten years this vehicle was in service, (2) add these ten numbers together, and (3) subtract this new total from the total original price I purchased the car for in 2010?... Would the result I end up with be both the "Prior Depreciation Equivalent" and "AMT Prior Depreciation Equivalent" that I enter for that vehicle?

I assume this is the correct way, but Publication 463 confuses me a bit (especially when it begins talking about "straight line depreciation".  Any insight or clarification would be very much appreciated.