Monster Damage Customizable

[LO1ZB]

Yea you use that to set the difficulty but if you use the debug screen in the latest snapshot you'll see that the numbers I mentioned:

But it is different. It is the Local difficulty. Local difficulty is the extra difficulty of a region. It's grow with the time you spend in that zone.

EDIT:

http://minecraft.gamepedia.com/Debug_scr..._.281.8.29
Local Difficulty Shows the difficulty of the chunk the player is in. See Difficulty on how this works. Followed by the amount of in-game days the player has been in the world, see Day-night cycle for more information.

That is true.
Local Difficulty is saved for each Chunk. When you spend time in an area, this area of the world become harder (more and stronger mobs)
http://minecraft.gamepedia.com/Difficult...difficulty