fuel capacity for 777-300ER from wikipedia: 320,863 lb / 145,538 kg
so let's say limit is 16h in the air that's 20053lbs/h or 9096kg/h
per engine that would be around 10026lbs/h or 4538kg/h.
now that's probably a bit high because it can stay in the air longer, not sure.
doing the same rough calculation for 7h of endurance of an 737-800 the 3000lbs/h seems realistic.
the 777 idle i would guess he is talking flight idle not ground idle.
but a much more pertinent question: why is this discussion in this thread?