I will try without pics. The tab that is extended from the adjuster is screwed tightly to the router on the side away from the rail in one of the guide-rod tapped holes, with the shorter supplied thumbscrew, so that it does not project through and bind the rod. The other thumbscrew (on the barrel of the adjuster is tightened onto the rod sticking through the adjuster. The other rod clamping screw, on the other rod is loose while making adjustments or not used at all if your cuts are not overly agressive. Make you initial cut to determine if your set-up is how you want it. Adjust your dial by the amount you need to and re-cut. For example, establish one wall of a dado (cut left to right) and note the dial position. Adjust the dial for the other wall and cut on the return. To repeat the cut, dial back to the original number for 1st pass, dial to 2nd number for 2nd pass. Each full increment is .1mm or .004". Splitting the increment is easy. (One Revolution is 1mm, IIRC) Locking the other rod is a matter of preference. I usually lock it for cuts and of course unlock for adjustments. I think this is the best of the guiderail router mechanisms Festool makes, IMHO.
I think John Lucas has some good Pics on this.
Greg