I really think this has to be a misprint on the initial spec sheet, like the LED brake lights (there are none). It's not like the exhaust bulge goes away when the seats are folded down, the floor is still 3-4 inches higher in the very back regardless. It should probably be exactly 3.1 cu ft. less, so 43.1 cu ft. for the sport models with the seats down. Unless the seats of the sport fold down lower somehow to make up for the bulge?I believe it's 3.1 cu ft. 25.7 cu ft vs. 22.6 cu ft with the rear seat up. But oddly enough, with the rear seat down, the area for both sport and non sport are the same at 46.2 cu ft3.