| A Ducati bulletin specifies that recommended tension for installing fresh out of the box new belts and the acceptable range of deviation (110 Hz +/-5Hz). It also states that if you are going to reinstall a set of used belts they should be adjusted to 90-100 Hz (+/- 5Hz). It further implies that used belts can be left alone if they measure above 70Hz.
What Ducati is saying is to first set the tension of a new belt to spec, expect them to lose a slight amount of tension after some initial miles, and then verify at any later time that this tension is above the minimum requirement. In other words, you should not re-adjust the tension to the new belt spec max after run-in.
Otherwise the belt will be in danger of snapping after a few re-tensionings. | 
Shazaam!
Threaded Mode