How can an appointment become available again for others to select?

Where are the appointments tracked? For instance, if I place a limit of 5 appointments per day but want to delete an entry so that it can become available again for others to select, how do I do that?

You can delete that submission from your Form submission page. By doing so, it will make that slot available again.

Here s how you can delete a submission - https://www.jotform.com/help/377-how-to-delete-form-submission-data

Do try and let us know if you have any further questions.