Update on Mac the jet black lab -mix

Mac has been with us for six weeks now.  He is a bundle of joy as a puppy and is growing with leaps and bounds.  We were told he was 30 lbs. when we adapted him.  Two weeks later he was 34 lbs.  Two weeks later again. getting his proper shots he was 43 lbs. Yesterday, he received his first of two Lyme disease shots and was weighed in at 47 lbs.  We were told by the rescue people and by our own vet he would probably be 80 lbs.  Not a problem our last dog was 75 lbs. of solid muscle.  Somehow I get the feeling Mac will be between 80-90 lbs.  Only time will tell.  He is a love though.