Can anyone explain this cap rate calculation methodology?

[Johann Jells]

This was part of our new assessment on a >4U multi. I can't figure out why they have anything about mortgages in their cap rate calc, I thought cap rate was on a cash deal, where you got it was your business. They basically just used our rent roll and this cap rate to come up with the assessed value.  Had they comped our lot as a teardown it would have been at least 50% more!