Run a night roll-call

Counting the boarders who should be in, and what to do about a gap.

The roll-call lists every boarder who should be on school grounds tonight — which is every boarder minus the ones signed out. You work down it marking who you have seen.

Anyone unmarked at the end is a gap, and the screen keeps them in front of you rather than letting the count quietly resolve itself. A gap is either a boarder who was signed out and nobody recorded it, or a boarder who is genuinely missing. That one is why this exists.