Signing up does not necessarily mean you are on the list. People on the waiting list will be treated as priority, provided they sign up next week.
Wait for a confirmation email
that will be sent before the event with the final list per boat, and a waiting list. From that moment, the skipper of your boat takes over responsibility.
If you become prevented from attending
You can before Monday click Usermenu>My Registrations> where you can change your registration.
After the mail is sent, you must contact the skipper.