this represents all of the desired events we want, which is rolling less than a 4 on a standard number cube (aka a die). There are A = 3 items in this set.
The sample space is the set of all possible outcomes, namely,
S = {1,2,3,4,5,6}
which is all of the values on the die. There are B = 6 items in this set.
Divide the values of A and B to get the theoretical probability:
You divide the amount of confetti cannons set off by the amount of confetti cannons set off every time there is a touchdown scored. So in this case 181818 ÷ 666