If used repeatedly there is a small chance the numbers on a card will change. The first, third and fourth can be either 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, or F, with 0 being the lowest and F the highest, and the second will be either a P or an M, and they can change to an X then an A.