With the "Automatically invite from wait list when space is available" option, you automatically invite (and reserve spaces for) people on the wait list when one or more spaces opens up. By adding a response timeout, you continue to invite the next person who joined the waitlist (automatically) if the previous invitee doesn't respond within a time limit that you set. With response timeout, it's first come, first serve amongst all the people invited, which makes this a great option to use to help fill the available spaces for your events. For more information, go to Manage the wait list.