Two ways someone who isn’t on the roster ends up in the headcount.
You add a recruit. From the admin event page, add a named guest to a practice. Use it for the person who came to a taster session and hasn’t joined yet, so the boat’s headcount is honest before you build a lineup.
A member brings a +1. A confirmed paddler can add a named guest to their own sign-up.
Both consume a seat from the roster cap, both show in “Guests & recruits” on the admin page, and both disappear from the form once the event is full. Guests don’t hold a paddling profile and never appear in the lineup editor, so anyone you plan to seat needs a real roster entry.
Guests apply to practices and race days. Team events use slots instead.