What do you mean by “how to read”? These are simple graphs. Say “Client Connections” shows that you have in average about 25 connections per day (excluding probably weekends, when it drops to zero).
As there is no legend, can’t answer that. This can be deducted only by testing i think, or by looking into source of that plugin. Plugin’s developer is not available anymore.
By comparing you graphs i guess blue one is the traffic from the group chats and orange is the simple messages. Just guessing.