Wolf Hunger?

How come I can have wolves all needing, saying 20% hunger and though I feed them food with multiple uses, some need one use for %20 to fill but others need 2 uses for 20% to fill?

I haven't found a reason for this.  (None of the wolves are pregnant or nursing that I fed).

Puppies eat less than adolescents and adults, so one food use will fill 20% hunger for a puppy, while one food use will only fill 10% hunger on an adolescent or adult wolf!