How about looking at the date the book you have was published? At one time it was actually thought that, because of the fast growth to a 'large' size by 6-ish months, it was proper to simply feed a dog by the average weight of an adult dog. That's not generally the case anymore - since nutrition for each breed is being further investigated by both pet nutritionists and observations of practical reality by breeders.
Your breeder is, and should be, your first line of inquiry for ALL questions relating to the health and well-being of a puppy. Your breeder should have given you information about feeding and growth for the first year (at least) of your baby; check there. If you do not have that connection with the breeder as a first resource? Well, then - find another breeder who has and will take the time to become your mentor in these issues. They are out there, and will help you if you come to them with "hey, I'm not able to get this from my breeder; can you help me?"
There is also VERY good information here, in the archives and from other folks who have younger dogs. Don't be freaked out by the argument about kibble versus RAW feeding - there are militant proponents of each method of feeding.
Do consider that you have a dog who by breed is a "swift grower" but a "slow maturer" and don't rush to put a lot of weight on your dog - the skeletal structures of a Newf need time to mature properly before they can carry the adult weight properly and work correctly.
Good luck finding your answers for your dog!
