Canned, homecooked, and raw foods have a significant amount of moisture and need to be converted to dry matter. Take, for instance, the frozen chicken Nibblets by Vital.
Protein: 11% min
Fat 9.5% min
Moisture: 74% max
Frozen Chicken Nibblets
On a dry matter basis the protein would be 42% (11/26).
The fat would be 36% (9.5/26).
Dry foods like kibble and freeze dried with low moisture content don't generally need to be converted to a dry matter basis because the difference is negligible. The math can be done anyway jst to show that this is true. So here is the guaranteed analysis for Freeze Dried Chicken Nibblets.
Protein 41% min
Fat 34.5% min
Moisture 8.5% max
Freeze-Dried Chicken Nibblets
On a dry matter basis this food is 44% protein (41/91.5).
The fat is 37% (34.5/91.5).
Below is a link to the AAFCO minimal percents needed for nutrients. Adult food has to contain at least 18% protein to be approved. The Vital 11% protein food is AAFCO approved. that is because it is more than 18% dry matter. If it was truly 11%, it would have never been approved. Anyway, the lowest % protein a dog can live on long term is thought to be more than 11%. If a company was only using 11% protein, those would be some really malnourished dogs... The food is mostly protein and fat.
AAFCO Dog Food Nutrient Profiles