Simple question: how to count doors?

[Matthew Copeland]

How do you count how many doors one owns? I get that if you own a sfr, that’s one door. But if you own, say 10% of a 100 unit apartment would say you own 10 doors or 100? But depending on your answer, if you have debt on the sfr, do you only own a percentage of that? So where do you draw the line? Thanks.