The procedures to reset the rear derailleur and derailleur to zero are essential for the system to function.
These procedures allow the system to learn the reference positions
of the chain on the sprockets and chainrings, which will be used to calculate the positions that need to be used in all operating conditions.
During the resetting to zero phase the movements of the rear derailleur and derailleur occur continuously, and not through set movements as during adjustment, and they depend on the pressure time of levers 2 and 3.
The position can be changed by even just a hundredth.