The distance from the wall is 6 cm, the actual depth of the radiator is 3 cm, so the maximum distance from the wall is 9 cm.

After checking the meter, I confirm Marc Mühlemann's answer! I would also like to point out that the distance between the wall and the radiator is 5.5 cm!

The depth of the wall-mounted radiator is 8.5 cm. But the control unit protrudes further at the bottom, so the total depth is even 11 cm.