Strange. Everyone I've told this to had the same measurement. You're not supposed to stretch it out as far as you can. It's more relaxed. And apparently, easier to show in person.
We're just playing with you a little. If I DON'T stretch them out fully, I can make them fit anything under 8.5" which might affect accuracy.
If we digress too much, the thread Nazi will get his shorts in a bunch.
Bottom line, we and most potential clients have SOMETHING or a set of tools that can be used to provide measurements to help us provide a quote. We present our clients with as many options to work with us as possible. If they want a quote right away and aren't right down the street or can't bring the vehicle to our shop, we instruct them to take some square on photos and overall width and height measurements of the sign, truck, etc. If they can.
In most cases, its enough to give us a good enough idea of what we're quoting on, but we're careful to Qualify our quote as being subject to change once we physically see the object, sign, installation conditions, surface, etc.
MOST are Happy to do so if it speeds up the process and possibly save them money.