Both the length and position of the strokes can be adjusted using the UP and DOWN buttons.
NOTE: You can read more about what the buttons does here.
If the Handy does not have full range of motion, where the length of the strokes are short, You can reset the device to maximum stroke length by following the steps below.
Steps
Keep the DOWN button pressed until the LED flashes red.
Repeatedly press the UP button until the LED flashes red.