Hi Jennifer and welcome to the forums!
I really wish the answer was yes but I’m afraid allowing visitors to submit the number of tickets available on the front end is not possible.
We are developing a way for this to work via the Community Events plugin, so please add your vote for the feature here and you’ll be updated as progress is made on it. It will definitely take some time before it releases, but this should keep you on the up and up. 🙂
Does this help answer your question? Please let me know.
Cheers!
Geoff