rushpaw:

Normally, medicine cats are the only cats in warriors who know how to count. It makes sense- medicine cats need numbers to prescribe exact doses, while the warriors pretty much only need to know if there is a large amount of something or a small amount. This is the reason medicine cats accompany leaders to their nine lives ceremony. It’s their job to signal when the correct amount of lives have been given, so no mistakes are made. This method worked without flaw for generations, however, StarClan forgot to take into account that Mothwing would not be at Mistystars ceramomy. It wasn’t until her 60th life or so that they realized their mistake.