Sorry, I didn't see this reply until just now. The grinding ring head (Trolley) runs on a fixed path, yes. If we say the grinding ring moves back and forth on the X-axis to sharpen the skate blade, the grinding ring itself is adjustable in the Y-axis by turning a knob, which has incremental "clicks." A separate height adjustment lever also allows Z-axis adjustment, so you can set the max height of the grinding ring. The grinding ring can then move downward from this setting with a consistent torsional spring pressure pushing the ring back up toward this max height setting. This puts consistent pressure on the grinding surface, taking off consistent amount of material along the entire blade's profile.
2 to 3 clicks of Y-axis adjustment is advertised to change edge height by approximately .001" when using a 1/2" radius ring. So in other words, they're telling us if your edges are off by .001", 2-3 clicks toward the taller edge should set them perfectly even. I work with Autocad and a quick sketch shows me that in order to get .001" height difference bewteen the edges on a 1/8" wide blade, the 1/2" grinding ring would need be approximately .004" off-center, in the Y-axis. So .004/2.5 clicks = .0016"; let's call it .0015" per click in the Y-axis. I also calculate approximately .0004" of edge height (Z-axis) adjustment per click (.001/2.5 clicks=.0004 per click).