"Limit Hunter" is not actually a official division; it's kind of a made up name for an unrated division or one at a schooling show. There is "Limit Equitation", which is open to riders who have not won 6 blue ribbons over courses of 2'6" or higher, and where fences are 2'6" - 2'9". The equitation divisions are maiden, novice, limit and open, followed by the various medal classes.
Rated hunter divisions start with fences at 3" (Children's and Adult Amateur); only ponies show over fences below that height (Small and medium working hunter ponies, and green working and confo ponies of all heights, I think, large working hunter ponies shows at 3'.)
So lots of shows offer unrated divisions for horses at lower heights, and they call them all sorts of things - Pre-green, baby-green, green as grass, open, schooling, student, etc, etc., and the show organization can offer them at whatever height they feel will draw entries. "Limit Hunter" suggests to me that the class is limited to horses that haven't won a lot at that height, which is cool, but the height can be whatever that show organization decides it wants.
Confusing, I know, but there it is.
Hope that helps.