UKC

This maybe a silly question but I will ask it anyway.
My local climbing wall is advertising a leading competition coming up in the next month or so and the advert reads its for leading 5+ to 8a. So how does that work then? Wouldn't some pro just rock up do the 8a and win? How is it judged ? I assume it split up in to ability groups but how is that decided?
I sure it's all very simple and I'm just not understanding it.

Please explain guys thanks

In reply to Scoldedcat:
If it the leading ladder there are 3 catogories
• A is for climbers who lead indoor routes in the grade range F5+ to 6b.
• B is for climbers who lead indoor routes in the grade range F6b to 7a.
• C is for climbers who lead indoor routes in the grade range F7a to 8a.

20 points for a flash, and counts down per attempt. No working routes. If you fall off restart.
Belay must be clipped while holding a hold and not the top of the wall or belay.

In reply to Chi Cheng: nice one thanks