You are able to set a limit on the number of participants that can register through a registration form. Once a registration form is full, any additional registrants will be put on a waitlist.
To set a registration limit:
Go to Registrations
Create a new form or edit an existing one
Click Edit on the registration group you wish to edit
Under the Registration Limits section, type in the Max Participants that can complete the form
Within the form, you can also set limits on other items. This could include an additional camp, ordering specific items with limited quantities, or registering for a limited number of spots volunteering.