600 grams is how big they can get, not how big they are in general. How long is your mali? If he is somewhere in the 11-14 inch range (snout to tail) he is probably okay at 240 grams. Note that I only keep Egyptians and this is all information I have read and talked to people about. Any other Mali owners have accurate weights of their adults? If he is eating well I would not worry much, he is probably just a bit skinny from the pinworms.