Our 7wk runt Cane corso.?

Is anyone experienced on what the weight should be for Rocco our 7wk old Cane Corso. We got him at 5wks at 5.2 ponds.(I know he was young, but the owner couldn't keep them longer) his is know 7wks and weighs 12 pounds. Is his weight about right. Let me know your experience on this. I don't want to hear he was still young and should be with Mom. Tell that to the owner, at least he has a good home i put him on puppy replacement milk and he is on Nutro puppy lamb and rice. He has more than doubled his weight with me in 2 wks. Thank you.