When you log in, or refresh, you can sometimes get a message saying something like "Congrats, you gained N XPs", or "Ack, you lost N XPs". That message is sometimes only half useful. What if you lost 2 XPs, and gained 7 and see a message that you gained N XPs? Then, it isn't obvious that you lost anything, which I think people tend to like to know. How about if the message said something like "You gained N XPs, but lost N as well."? That would just be more accurate.