Note: It's important to look up how to calibrate in your machine's user manual.
Each stylus contacts a reference point on a calibration sphere. The data of the exact dimensions of the sphere being calibrated are put in the measuring software. If calibrating multiple styli for measuring separate points, the stylus is calibrated with 5-6 reference points on the calibration sphere. In scanning systems, many more numbers of points are used. For precise probing strategies, see your machine's user manual. Make sure the correct data for your calibration sphere is in the software for your machine.