hi,
that measurement is overall height of your van.
normal size for most vans is Height: To fit caravans from 225-250 cm(app 7ft 6'- 8ft 4') awning rail hight(this covers majority of vans).... measure from ground directly up to awning rail centre.
some vans have a smaller awning rail height than others,avondale one time were one of the manufactures with the boat type roof where the awning rail(like my osprey was) only 7ft,so best to measure first.