What's the enlightenment of cutting some cartoons in pizza?

Don't stick to form. This is a funny cartoon in America. She was asked to buy pizza. The clerk asked her how many pieces to cut, and there were eight pieces and 12 pieces to choose from. Let her choose a few pieces and explain the reasons. My sister said that cutting into eight pieces is because 12 pieces are too much to eat, but no matter how many pieces are cut, the total amount remains the same, which encourages us not to stick to the form.