Comment by brudgers

Using a knob when using a knob doesn't solve the problem is poor design...then again, skeuomorphism is usually bad design.

Here a counter that increases and decreases with mouse movement would take less space and be more intuitive.

And a much much better design because it would provide a numerical readout of the value directly at the point of interaction.

But in fairness, most design is bad because designers tend toward satisfying themselves rather than users...ok, I will stop ranting now.