If you are tapping a small endmill, 8mm or 3/8", and keep getting double hit errors, you can override this feature in order to get a measurement.
1. Click the Setup button
2. Click on the Sensor tab
3. Uncheck the box next to Trap Double Hits
4. Click Apply
5. Click OK
Now redo "Practice" and tap the tool. Be sure to go back and recheck this box, apply and ok after you are done tapping the small endmill.