clients sending large amount of data to SEP server

It seems our clients are sending a large amount of data to the SEP server. Last night for instance we observed one client that sent 1.2 GB of data to the server. I think this was after a new/fresh install of the 12.1671 client version.

We do have a GUP on that site, which I think helps reduce traffic from the SEP server to a local server and then to the client, but not the other way around.

Is that much communication normal? That seems way out of line with what I would expect.