Ya but they showed the light penatly wrong. the +2 would cancel out the -2 to net a 0 attack penalty from the rank 2 monster
I think he said it correctly.
the video wrote:
This is where light comes in.
If you have a torch which gives one light, and you are going in the dungeon with a wizard, who also gives you one light, then those two light points remove the two light points from monster you are fighting.
He probably should have finished by saying "The new darkness penalty is now 0*2 = 0."
His equation on the screen shows:
Total light = 2
The text on the screen never shows the value after the light and darkness negate each other.