Personally I'd weigh the 2 cups and figure it out that way. I think nuts and seeds are by weight not volume? You could use all your nut servings as flax bread so whatever it works out to. I don't have any flax meal right now or I'd pull my scale out. Someone let us all know please
ETA - I always assume that when it says cups/Tablespoon it's volume and oz or lb is weight.