You mean 6 megabits i think, which is an 8th of a megabyte. (there is 8 bits to a byte)
so 678kBp/s(kilobytes) x8 = 5424kbps (kilobits)
so 5424kbps out of a possable 6000kbps/6megabits (download very rarely max out a connection and needs some of your connection for overhead)
so you are getting the full 6 megabits more of less.
So think yourself lucky i can only get 1megabit no matter how much i pay where i live