what is the difference between 2 clicks, a few mm?
I'm just going from memory, but let's try a bit of a thought experiment: if the adjusters have 1mm thread pitch, and if there are 16 points to "click", then 2 points is 1/8th of a rotation; that's 1/8 of a millimeter of (roughly) the circumference of the shoes. Divide that by PI, and two clicks means that the shoes change their diameter by 0.039mm - that is roughly half the thickness of paper, and half of that is on one side of the diameter, the other half is 180 degrees around the drum. The shoes ride VERY close to the drum when properly adjusted.
So two clicks is roughly two hundredths of a millimeter between each shoe and the drum! Even if my guesses were wrong, they won't be too far off so the general notion of a very small distance is still applicable. This is why brake adjustments are needed, it does not take much wear to change the spacing and require that the spacing be put back to what works well.
And there are what the parts list calls "static pressure valves" under the master cylinder that keep the shoes from retracting too far, too fast. So if you need to pump the brakes first thing in the morning, they need adjusting. Once they are "pumped up" they they only retract enough to allow the drum to turn; so braking again in short succession will usually NOT need pumping again. But if they need pumping at any time, adjust them properly.