RickRR: I can only assume the calculation is a little off.
It's not about your calculations being off, they're never going to be exact. That's the nature of golf. What's important is that you learn how the club's carry plays for each situation you face. You don't get the exact same shot every time and your clubs aren't exact-you're playing to favorable areas that make the next shot or putt easier.
Picture what a successful shot arc looks like in your mind's eye. Picture how you want it to land and roll or stick and then think which club is best suited for doing what you want. You should have 2-3 different ways to execute particular yardages and when you have those options, each shot becomes a decision on which shot to use. You already know your carries, how do the variables affect what happens next?
I'm a "feel" golfer like a lot of others are. I can't be bothered with charts and spreadsheets, et al. Simple math done in the head and then pick a club. I don't even think of whatever the caddie is offering, I already know what I want to do. I can get away playing that way simply because my clubs carry their rated distances with the ball I use. It lets you be a lazy golfer, like me, and play instinctively. ;-)