The "number" in the model number most manufactures use seldom has anything to do with the actual length of either the "box" or the overall "bumper to ball" length. The dimensions given by the manufacturer in the brochure is probably more accurate, but you never know whether they are including everything or not - bumper? spare tire?
Our JayFeather 29N measured 29'11" overall, and our Outback 277RL measures 34'10" plus the spare tire. Go figure!
As stated above, the only way to find out for sure is to measure it.