Regardless of how spot on your shirt order is, chances are you'll probably have shirts left over after your race, either because people didn't show up or because your size guesstimates where a bit off etc.
That doesn't mean your leftover shirts are a waste though. There are several things you can do with your leftover shirts, from recycling them or donating them to a charity or hospital, all the way to selling them in your merch store or giving them away in a "lucky dip" race - all ideas we discuss in much more detail in a whole different article.