Door opening height is specified separately from inside height. If the inside height is said to be 7 feet, this does not mean the door clearance height is 7 feet. Many openings are 6 inches lower than the ceiling height. Also, keep in mind that depending on the angle of your ramp and if it is going to have a beaver tail, you may need more door clearance height than the actual height of the item you are loading.
MAKE SURE THAT THE DOOR CLEARANCE HEIGHT YOU NEED IS CLEARLY LISTED ON YOUR ORDER.