Forum:Prime Material Dragon's effect

Hi, just wondering about the REAL effect of Prime Material Dragon. You see my friend and I kept arguing about its effect. Last time when we dueled, he has 2 Prime Material Dragon's face-up on his field. When he attacked, I activated Magic Cylinder. So because of Prime Material Dragon's effect, he will gain Life Points instead. But he also said that he will gain 4800 Life Points because of both of their effects. I said," You will only gain 2400", but he kept insisting he will gain 4800 because of both of their effects. So which is which?