Pizza Math
Counting act associated with sharing pizza between two or more people. As the number of slices diminish those desiring more pizza will attempt to count how many slices each person has consumed in order to figure out if they can legitimately claim the last slice of pizza (usually not wanting to look selfish or like a pig).
I was going to grab the last slice of pepperoni but I did the pizza math and I'd already had more than everyone else.