If I’ve read that right I should take out at around 49degrees then let it rest and then blast it for 10 mins meaning it should be around 52-54 degrees when serving?
Depends how you want it, I think a Rib is best medium rare so that the fat renders enough. I normally take mine out at 53 and then put back in the oven on max for 5-8 mins (not enough to raise the internal temp).
If you're going Rib of Beef I can thoroughly recommend cooking it the Serious Eats way...
It's fail proof and definitely the way to go, we had a lovely joint a few days ago cooked this way.