A lot of authors explain their calculations in the book somewhere. I always enter the amounts as published, then in the notes list the published OG, IBU, HBU, etc. This keeps me a clean copy of the original, as published, but allows me to tweak it to match my equipment when I brew it.
I am also helping some young brewers getting started, so I can also tweak those recipes to match their equipment profiles.
It's a great learning experience to enter recipes from a book. It shows how others formulate recipes, and how little changes can alter your beer.
It also gives you pratice with BeerSmith.
On a related note, I had 100+ recipes I had collected over the years entered to match my equipment profile. Then SWMBO bought me a new mash tun for my birthday, and, like your problem, none of the numbers in my recipes added up anymore.