It's foundry tactical combat. It shows your dps, hps and damage taken per second in that order from left to right.
Is it based on the last combat or all of the combats is the session you are playing?
It updates per encounter. So if you attack a group of mobs and kill them, you will see the stats for those mobs. If you wait a few seconds and then attack another monster, the stats will reset and only show what you have done against that monster.