Once an account has clicked the Job Signup button for an event and signed up for a job, the button will change to Edit Job Signup. If they remove their job signup at a later date, the button will revert back to Job Signup. This is a quick indicator to the Account that they have signed up or not signed up for job(s) for that particular event.

See Also
OnDeck Coach University: Job Manager
How do I email Volunteers signed up for jobs?