Free extra food!

So this is the second time it happened to me. I haven't been in Burger King in a year, I ordered two spicy chicken sandwich meals for my sister and I. I also wanted a second sandwich, I didn't have enough. Then the cashier brought the bag over to us and said, "I put the two extra sandwiches in there don't tell anyone. " she was sweet and deserved a raise.  The other time was at a pizza shop I ordered two slice he gave me four. ???