Hi-Lo trailers are measured from the tip of the hitch to the back of the rear bumper.
Other manufactures measure the box for the trailer length.
Need more information, the box lengths vary from 6 to 9 inches depending on year, model.
MANY campers are measured from Tip of tongue (hitch) to bumper. so if we do some guessing, 20ft sleeping area, plus average of 3.5 or 4 ft of tongue, you probably seeing it called a 24ft camper. My Scamp fiberglass camper was measured the same way. Yeah, kinda like saying 15 &17 inch monitors back in the day, ya know?