direct file download, not a torrent, etc?
I usually find mine is pretty accurate.. within a probably 50mb maybe +/- per day (but thats with an around 2g usage per say, so in the end a VERRY little varriance).
Rogers JUST released some new plans today..
Depending on your current package.. and other services you may have.. they do have some promos, which include EXTRA usage right now.
(i was able to drop my unlimited usage, for a +200gb addional)