Quadruple Fives

Tonight, Grant and his brother were playing backgammon while I researched Ayurvedic stuff on the internet. His brother was completely smoking him and had about one roll left before the game was over. On Grant's next turn he yelled out "quadruple fives!" His brother responded, "if you get it, you win." So Grant took his brother's dice, shook all four together in his hands, and lo and behold... he actually rolled quadruple fives. Someone please comment on the probability of that happening and don't forget to factor in that he called it.

I wonder what else he knows...