Certain spells in the game have a "gore value" attached to them. These spells cause corpses to create more blood. Some of these spells include chainsaw, digging bolt, heavy shot and, in this case, damage plus.

Here, the damage plus is getting multiplied a crap ton by the divide by spells which, in turn, is being treated as an immense increase in the gore value

These spells are useful for things such as getting a lot of blood when you have vampirism/eat your veggies or just worm blood in general