One thing on your f250 is that it's rated by the door placard....
if it says 10000 I very much doubt they put a greater than in front of it
Maybe someone was helping you out ?!?
Depending on your cab style (crew cab, super cab or regular cab) and engine (gas or deezle) then unhooked you are probably at about 5000 on front an 3500 on rear so say 8500 - if your placard says 10k you can only add 1500 lbs period for the TOTAL weight and yes, on the rear only maybe up to 6200 rawr, but then it puts you WEIGH over your gvwr - so it's a tough one....
and never count on the truck salesmen to tell you straight !
in fact, I'll go so far as to say they don't WANT to know so they don't have to tell you something that may stop you from buying that truck !