as far as the question goes... just round it off... 300 gpm to pump 48000 gallons... 160 minutes... probably close to correct if including time to connect, ground, disconnect and such and no other issues..
I was under the impression that airlines will take on enough fuel to get where they are going.... as weight is cost... and dont necessarily fill em to the brim... maybe I am wrong but I don't think they fill em up if they don't need to...
which reminds me of the scene from Capt Ron, where he runs out of fuel and he exclaims that he cant be out of fuel because he put enough in to get to Cuba and they weren't in Cuba yet.
Just to complicate things, they're only so big (10,000 gallons seems to be about as big as they typically come), so they probably need to bring in a new refueling truck.