The word crude indicates that this number is for both digestible and undigestible protein. What is digestible protein will vary depending upon the ingredients and their quality. That's why the crude protein figure is only a rough guide. Likewise, crude fat is the minimum amount of fat contained in the diet, before the dog metabolizes the food. Crude fiber is the maximum amount of raw fiber in the food.
Moisture is the maximum amount of water in the food.
The amount of moisture in the food can become an important factor when comparing foods. To compare foods equally, you must adjust for the amount of moisture. The Guaranteed Analysis provides minimums and maximums. These are the guidelines which set the limits, but the actual numbers may vary. Quality of the ingredients may vary, too, depending on the season, the source, and the supplier.