Press button h. Each pulse on the button will obtain increase by one unit. Automatic fast increase is obtained by keeping the button pressed for few seconds. When you are near the required value, release the button and complete adjustment with single presses.
See also:
Spark plugs
The cleanness and soundness of the spark plugs are very important for keeping
the engine efficient and polluting emissions down.
The appearance of the spark plug, if examined by an expert eyes, is ...
Controls
(A): Air temperature knob (mixing hot and cold air);
(B): Air recirculation on/off button;
(C): Fan knob and climate control system on/off;
(D): Air distribution knob. ...