I registered just to try and remove a couple things from the possibilities. I too have a router that counts data, and I too see a huge discrepancy in data usage. This month comcast has be using over 50 GB more than what my router says. Its definitely not TV usage (i don't have TV) and its not wifi usage (I don't use their modem/router with their xfinity service broadcasted). There's no way there is that much data in header information either.