You may have a listing set as a Public Event if you're seeing open spaces although you're fully booked.
In the screenshot above, you'll see it says "Public Event." This means multiple parties can book until all spots have been reserved. If you have 10 spots available, and your listing is "public," then 10 people from different groups can book until it's full.
If you want your Listings to be private, so only one group can book, simply deselect that box.
