This image was from the form when the admin created the mission
This was a system from an old group that I was part of, it works as follows.
The admin registered a new game and added the vacancies available for the member to sign up.
In the page of vacancies had some information like date and schedule of the game, a brief description about the game and a picture and the places for the members to subscribe, but when a member registered in a certain vacancy that vacancy would be unavailable to the others.
It worked as a kind of hotel reservation but with only 1 seat