I'm not sure how to answer that.
I have 7 inside. Some have been here for up to three years, but if I had a home for them, I'd gladly give them up. (Well, maybe not ALL of them ;) ).
And then there are the 8 outside that were abandoned. I've been feeding them (after neutering and shots) so they are technically mine. But I have no room to take them inside. When they get a little less afraid of people, they will need homes.
And there are the 3 neighbor cats that spend all their time on my porch and join in at mealtime.
You figure it out; higher math isn't my forte.