"There is no car. The 18,500 is equipment used in the business."

It's only 3 years prior to the one you are working on. It's not so far back that you cannot get Bank records. It's not so far back that this person should be able to remember what these few assets are. It's not as if you need to reconstruct Corporate start up with a warehouse, an office building, completely outfitted, including rolling stock.

If you build the info and the math still makes no sense, they likely did it wrong. If what you have is what the IRS got, that seems pretty easy to determine.