For example, p is the permutation number and c is the combination number.

P is 5 below and 3 above, which means that three ordered arrangements are taken out of the five elements, and the value is 5X4X3.

And C53 means taking three of the five elements to form a group, which is equal to 5x4x3/3x2x 1 = 10 if there is no order.