Add higher half-ages

I am interested in updating the age limit for certain classes, as our studio has 2 terms wherein students must sign up for classes again to complete the rest of the year. Classes that had an age limit of 5 allowed students who were 5 years old to sign up. Now that students must sign up again, some students within the age limit are now 5.5 but cannot sign up because of this. We don't want 6 year-olds to sign up for the class, just 5.5 year-olds! But the half-ages stop at age 5. They should continue until age 10 for sure.