I did some Googling, and everyone else seems to be going through no more than 200 MB per hour on large servers with many players, whereas I am on alone or with only 1 other person. From what I can find, I shouldn't be going through much more than 40 MB per hour.
Im p sure data usage is dictated by various other processes too.
You are Implying the following:
1. You only had minecraft open.
2. The data was not being used elsewhere.
3. That the data shown is factual.