joystick sensor in game engine

what is actually the difference between axis and single axis in the joystick sensor in blender? i think there are 8 different axes to choose, and 16 single axes. but what’s the difference?

If you use singel axis you can only chose the axis (horizontal), so the pulses come out from the sensor when you move your joystick left or right. If you use axis you can chose only one side.

Single Axis