First of all, the term “hydrostatic” just adds black magic to a stupid simple self adjusting system. With the self adjusting version, the slave piston when at rest has 3/4" of free movement to the front of the car. Because of that, it exerts essentially no pressure on the actuating lever unless the clutch pedal is depressed. All the return force is supplied by the clutch itself: the clutch springs or diaphagm push back on the release surface. Travel is limited by the mechanical limits of the clutch mechanism. At this neutral point, the release bearing is just touching the release surface. It doesn’t turn, because it’s a graphite donut, rather than a true bearing. With this system, the release bearing can wear since it’s always in contact with the release surface. And mechanics, confused by the various procedures and parts supercessions can set it up incorrectly and cause premature failure.
Your setup isn’t self adjusting, at least, it wasn’t intended to be. The clutch pushes the beariing back to a neutral point, as with the self adjusting system. But the external spring which is in your photo pulls the arm slightly forward of the neutral point, to lift the bearing off the contact surface. As the clutch wears, the release bearing is pushed further back, and so you have to adjust it from time to time to restore the gap. To check whether you have it it adjusted correctly, your best bet is to sight the release bearing through the port in the bell housing. The exact gap is less important than whether there is a gap…no gap means wear is likely.