Adding a support act, what a bill commits you to, and why a shared night counts differently.
Open any night and there is a bill on it: everyone playing, in the order they play. Add another act and you get a second slot on the same date at an earlier time, which you book like any other.
A support slot takes the night's kind — one door, one admission — and the running order is simply who is on when.
This is the part worth reading. Every revenue split on a night is a percentage of the same door. Two acts on sixty per cent each is a hundred and twenty per cent of the door, and you would be paying the last twenty out of your own pocket.
The bill adds them up and says so. It also flags the case people trip over: a flat fee feels like it comes off the top, but a split next to it is still a percentage of the whole door, not of what is left after the fee.
It warns; it never refuses. Giving away a whole door for one night is a real decision — a loss leader, a favour, a launch — and it is yours to make. It should just never happen without you noticing.
Nobody's, on its own — and that is deliberate. When several acts share a night, the crowd came for the bill, and there is no honest way to say how much of it each one brought.
So a shared night counts toward your room's history but toward no single act's draw record. Crediting each of them with the whole room would make three acts all look like they drew two hundred people, and splitting the crowd evenly would invent a number — a support act who brought nobody would come out level with a headliner who sold the place out.
What still counts is tickets each act sold themselves. Those really are theirs, and they are exactly what tells an opener from a headliner on a shared night.