"Percent moisture" refers to the amount of water present in something, usually measured as a percentage of the total weight or volume. It tells you how damp or wet something is. Full definition
Most people accept the figures given on the label for kibble because the 10 percent moisture doesn't make a lot of difference to the dry matter figures. (dogfoodinsider.com)
This food is «in gravy» which accounts for the 82 percent moisture of the food that comes from the tuna broth. (kittycatter.com)
Kibble usually contains about 10 percent moisture so you can do the calculations to figure its dry matter basis, too. (dogfoodinsider.com)