Dog and cat food ingredients are written on the ingredients label based on their relative weights before being cooked. Let's try an example: "Chicken, Chicken Meal, Rice, Barley." If you were to weigh out all the raw ingredients of the example, there would be more chicken than chicken meal, but that's not the whole story.
Like we said, these are ingredient weights before cooking. Did you know that a piece of raw chicken is about 80% water? Well dry dog food has only about 4% moisture content. That means that when we cook 10lbs of raw chicken into kibble we're left with only 2lbs. Chicken meal on the other hand is a raw ingredient in dog food that was already cooked and ground before being added as a raw ingredient. So it will lose hardly any moisture weight when the kibble is produced. In the example we gave there is actually more chicken meal in the finished product.