While Mike responds:

If the grey horn (aileron neutral) is perpendicular to the center line of the aileron, there is no differential there.

As shown in neutral position, the same angular deflection (number of degrees of rotation) of the servo, will induce more angular deflection of the aileron in the up direction than in the down direction.
Kind of the same effect that the first schematic shows, but in reverse.

Note that this configuration applies to a low wing airplane.
For a high wing plane, the deviation from the perpendicular position for neutral should be on the opposite side.

This differential can be used alone at the aileron horn, or combined with the differential at the servo (in order to multiply the effect).