dling

how? i have a 512kbps speed conn. and get 50-55kbps while downloading the torrent which i am DL'ing has 26-30 seeders and 7 leechers no replies?

on my 749 NU i start DLing at 12 15 and stop at 7 45. today morning i saw my used mbs were 250 or so now i checked they r 449 MB. What the hell is happening?what should i do?? and yes i do reboot my router with acchablog method. pleaseeee help guyz. what time i shud start and what time to end DLing?