check this link and get an approx idea of your Data usage.
Evn though the calculator is used for cellphones/etc
for adsl line also can be used as a rough guide.


for example see this:
How much data is it for Smartphones?(android OS)
Email (text only) = 10 KB
Typical Web Page Lookup* = 400 KB
Audio Streaming = 40 MB/hr
Lo-Res Video Streaming = 200 MB/hr
Hi-Res Video Streaming = 400 MB/hr
Digital Photo download/upload (Hi-Res) = 1 MB

http://www.verizonwireless.com/splash_i ... lator.html

Para two:
BSNL users : The reading/s in BSNL meters are final.
Post for details of other bW meters bsnl portals being prepared.