We have one (AllHandsActive.com - Ann Arbor, MI). Ours works slightly differently than what you said. The knob on the front limits it. The software limits it further. When running if we set ours to 15MW (on the knob) and set 50% power in software we get ~7.5MW read out on the gauge during the run.
The software (RetinaEngrave) is pretty terrible. It does make multiple passes and splitting colors (different power/passes) easy, but alignment of raster and vector images is a pain. It also only seems to consistently open
Good machine though. Works well otherwise.