Just as a comment... This question could have been easily answered in the other thread you had going.
By a show having divisions, they can break down the horses/people into groups, so that it is more fair. Kids vs kids, adults vs adults, green horses vs green horses. It wouldn't be very fair for a little short stirrup kid to be competing against an Adult Amateur. Sometimes in a large division (50+ horses for example) in an adult class, they will make the age divider 35. So 18 to 34's will compete against each other, and those over 35 will compete against each other. (Easy example, not necessarily true!)
The numbers you see below the division are the class numbers. The pre-Green division will be made up of class 22, 23 and 24.