Subnet view shows statistic for the specific Subnet in the specific Traffic Pattern.
To see traffic statistic for an Subnet, go to TopN > Traffic Patterns option, select the desired Traffic Pattern and then the desired Subnet.
The Navigation Tree in the Menu Panel shows Subnets of the selected Traffic Pattern, while Main Panel shows traffic for for the selected Subnet (throughput or volume, in bits, packets or flows). Clicking on any tab option will show traffic distribution by that category (e.g. clicking on the Host tab will give you top hosts for the selected Subnet).
Figure above shows service Facebook Traffic statistic for the US colleges. You can see that X.X.205.155 host was the major Facebook bandwidth consumer and that the most of the downloads (In traffic) occurred between 9 and 10 AM.