I have a donwload limit how much would a xbox 360 use of that in a average online multiplayer game?

it a wide question to ask i know but any knowledge would be help full, but more specific would be playing a online game on gears 2 or call of duty 4 im often host as i have good download and upload speed, im just curios as i have a download limit of 40gb so i get a better than average consistence with my speed never usually drops below 7 and half meg and i speed test this on the same server every day, with only one device connected to test. i mean we must be talking kbs or at the most mbs but how much