What you should know about attendance
Event attendance comes in two different flavors. The event's hosts can select one of two options. There's automatic and there's manual.
Here are the fundamental differences.
When a host configures an event with manual attendance, all the users that want to attend will "reply" signaling that they are available. When a user is set to available it will not count to either the slot limitations or the attendee list.
At this point, the hosts will be notified of newly available users and will need to manually approve each one, confirming their presence for a given event.
When the event is configured in this fashion, the users that "reply" in a positive manner, will have their presence confirmed automatically setting their status confirmed. This will be possible only while there are slots available.
In the event that there are no more slots, the user will be set to available instead of confirmed.