The ashes that you find on the product label are the remains of the food that remains after its incineration. It is the final product of food combustion, where only mineral substances remain, such as calcium, phosphorus, zinc or iron, among others. It comes mainly from the bones of the raw material with which the food is made, but it varies a lot depending on what foods are used.
The ashes contain minerals that are very useful for the development of the bones and tissue of the animal. These types of substances will prevent a mineral deficiency in your cat, so they are highly recommended.