When you sign up for a waitlist, a credit will be taken from your account. As soon as a spot opens up, you will be automatically booked for the workout (up to 8 hours prior to the class, so be ready!). This means you don't have to check non-stop if a spot is available, yesss! When a spot opens up within 8 hours before class, you get a mail to sign up. First come, first served!
Good to know: you can remove yourself from the waitlist. Oh, and Premium members have waitlist priority.