So, apparently I was right. A steak cooked in a pan gains approximate 10c/18f while resting.
I have never understood nailing this down to an exact number.
I understand a steak's center heats up as the heat within the steak itself (hotter at the outside where it has been in contact with the pan, cooler on the inside) normalizes and becomes more uniform (entropy!) but how much the center heats up is dependent on the size of the steak.
What does your fancy book have to say about it?