I asked the dealer and he said what you explained in your last reply.It could be a design difference from the manufacturer. In the lower end models like 540A they adopt a linear scale and higher end ones like this it must be a non linear scale.
In a non linear scale, you get more control in the lower part of the curve. So no need to worry, at -22dB you have lot of headroom to go. Enjoy the music!
You can always ask the dealer if this is normal with this particular model, if his answers are not reassuring, you can return them