Do people always spend increments of 15 minutes in a room? Can they run through a room to get to another room? That is, if the map is A-B-C, can they be in A from 9:30-9:45, run through B, then spend 9:45-10:00 in C?

    Dave said: "I saw nobody when I was leaving the living room at 10:30"

Does this mean no one was in the living room when he left it? Or does it mean no one was in the room he entered when he entered it? Or both?

What is to stop a person from being in multiple rooms within a 15 minute period?

If a person exits a room at the same time someone else enters it, does either see the other?