Tower War Hero Percentage

Does anyone know whether the percentage next to the heros name on war is their bonus percentage for fighting you or if that is how much more power you have than them?

That number is the percentage of their actual power you will be facing should you choose to fight them. So for someone with, for instance, 6mil power and 50%, you would fight them as if their power were 3mil. That percentage depends on the difference in level and/or power between you.