Posted this on the Events API page (http://nationbuilder.com/events_api) but thought I should post here as well:

For the guests_count parameter, what is the API referencing? When you create an event, you have the option to do a simple RSVP and include +1s. However, if you have ticket sales, you purchase a number of tickets. Does guest_count reference +1s or number or tickets, or both? Ideally, it would great if it’s both!