No such thing as a dumb question! Here goes, the 7 and 8 refer to the category of chassis based on gross vehicle weight ratings. The size of an expeditor are broken down into the abc. An "A" class unit would have a load capacity of approx 500 lbs., a "B" would also be a van like a 1 ton unit capable of hauling that 2000lb. load and the "C" unit will have the capacity to haul 5000lbs., A "D" unit will be in the 13,000lbs and will depending on equipment may require the truck to be outfitted with a tag axle or a tandem rear axle configuration. And lastly the "E" unit is a tractor trailer, hopefully will able to legally scale 44,000lbs. Thats about it, hope this helps with the confusion. Good luck and keep us posted if you take the plunge into expediting. I've been on the road for 30 plus years and this is by far the best place to be! We all want to help you and unlike other industrys are truly happy when one of our own "Makes it Big".