Based on the standard game difficulty settings how do these % apply? Is it applied to the enemies base value? Or is it applied on top of the difficulty slider?

For example, on master enemies deal 2x as much damage. So if I give undead a +50% to damage does this mean they'll deal 2.5x as much damage? Or would it be more like 3x as much damage "applied to their base value before difficulty adjustments are applied"