There's currently no way to tell if the network traffic shown in the chart comes from Internet or from one of the VPC peered networks.

It would be interesting to be able to see the network traffic for each VPC and public internet so spikes on network activity could be easier to investigate. Also would allow migrations of networking configurations to be visualized and validated easier. As of now the only way I found to do that was to check the database access history to see the source IP of the clients.

Also, I was thinking that likely Atlas does the network peering outside the server but the networking chart information is taken at the server level. If that's the case one halfway solution to this issue using only data available at the server would be to draw the network information split into two types of network activity: traffic where source is a public IP and traffic where source is a private IP (minus all system network for sure). This would help at least visualize the difference between any VPC traffic and internet traffic.