If an event attendee cancels their event registration, and staff marks the candidate's event record as Cancelled in their EMS profile on the Record tab, it does not delete the registration. This is an issue with schools that have a maximum attendance for events, because it doesn't open up those slots for others to sign up.
It also doesn't work the other way, where if a registration is deleted from within Event Management it isn't noted as Cancelled on the candidate's EMS profile.
Ideally these would talk to each other and if it is cancelled in one place it would be deleted in the other, and vice versa. It would also be helpful, further down the road, to have the ability to select which attendee is cancelling from within the EMS profile (see idea K12OB-I-2811) so that attendees could be removed from either an EMS profile or from an attendee list in event management.