The ashes that you find on the product label are the remains of the food that remains after incineration. It is the final product of the combustion of food, 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 quite a bit 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, which is why they are highly recommended.