Live
Capacity during the show
The only place the number you paid for is enforced, the headroom above it, and what a guest sees if the room is full.
Your capacity limits one thing: how many phones hold a live connection at once. It does not limit how many people can open your page, read it, RSVP or watch your reel. That page is public and stays public.
There is real headroom above the number, ten percent plus fifty connections. That is not generosity, it is the cost of reconnection: a room with patchy signal has people dropping and rejoining constantly, and counting each rejoin against a hard ceiling would lock out the people already inside.
Image
The capacity stepper in the settings panel during the live phase.
Raising capacity during a show works, up to a ceiling tied to what was actually reserved for you: ten percent above the provisioned load, or ten more connections, whichever is larger. Past that the machine your event is running on would have to be bigger, and that is not a mid-show change.
A guest arriving at a full room does not get an error. They get the same soft path as someone outside a GeoFence: the reel, without the live channel.