think i may've worked it out.
using a bits/bytes conversion calculator i've found that in a 30-day month, i'd be able to use 107,373,333 bytes (about 102mb) worth of data, per day.
i've now been online for just over 5 hours and i've sent 4,324,220 bytes and received 27,704,098 bytes. way less than what i've worked out to be the daily limit. but i could be completely wrong, lol.
like i say, i'm a beginner so, please keep me right.