Questions about waitlist! Please help

so I really want to get in this marketing class, so far it shows
Class Capacity
35
Enrollment Total
34
Available Seats
1
Waitlist capacity:15
Waitlist total:5

So my waitlist position is #3, its a summer 5 week class. Why my position doesn’t advance to #2 since there is 1 seat available?
And I’m a senior student so I’m not sure how waitlist works does it depend on my GPA? whats my chance of getting enrolled in this class?