How much dice does a Dwarf gains with the Grudge race ability of the Dwarves when he battles a Greenskin that has wounded him?

A good question, we've allways added only one fortune die and thought that when the dwarves have grudge against anyone they get that bonus. Ween they are wounded they get this grudge bonus, but for greenskins it's allready in place from the start.

But the wording in the rulebook could go both ways I think. So I guess it's up to the GM, but I think we'll continue to just add the one fortune die.

By the book I would say that if it was supposed to stack, they would have said that it does. It's your game, though, so go for it if you want.