So on this, I decided to monitor my own AMP client (windows machine) for a day - used Netbalancer v9.12.4.
The results are as attached, about 9MB of download and 6MB of upload.
These are not fixed values, of course, as each person downloads, and uses their machines differently.
The more files and processes you have running in a machine, the more reporting it has to upload, for instance.
