A/O Jumpers?

Okay so I was wondering what the deal with A/O Jumpers is. I know it's Amateur owner and that means you can't ride in it if you are a professional, I think? Haha, I was mainly wondering how high it is. I'm aware there are low's and highs. If someone could inform me on the height of both these classes? Thanks ;D

Amateur Owner means that yes, you have to be an Amateur aka not a Pro and not under 18yo. And you must Own the horse, no leasing.

Low is 3'11"
Med is 4'3"
High is 4'7"

Oh my god that's so high D:

High AO: 4'5"-4'9" with spreads no greater than 5'0"
Low AO: 3'9"-4'3"

Amateur Owner Jumper: A horse that is ridden by an Amateur Owner or an amateur
member of the owner’s family. In either case, classes are restricted to riders who are no
longer eligible to compete as junior exhibitors. Leased horses are not eligible, and multiple
ownership is not permitted unless all owners are members of the same family.