A calibrated set is when you purchase more than 1 pickup for a single guitar at the same time, and they are voiced to match their particular position on that guitar. You don't need to specify 'calibrated'; as long as BK knows you are putting X in the bridge and Y in the neck of the same guitar, and what the guitar is, etc, they will be calibrated to match.
Typically, though, calibrated sets refer to a matched set of the same pups in a guitar; ie, Miracle Man in the brige and neck of the same guitar.