The red graph shows data uploaded. The plateau is me sending an email with a few differnt attachments. The yellow spike (data downloaded) is when I checked my sent items folder and my email client had to download that same email I just sent from the server.
The graph doesn't ever zero out because I have Windows Picture Manager open on a file on the network and for whatever reason that constantly uses a small amount of bandwidth.
If you thought that was exciting, you should watch CPU usage! If you didn't think that was exciting, you probably weren't the only reader out there with that thought.