From memory. The pin that goes into the slave cylinder threads into the release arm, and there is a lock nut to secure it. So in effect, you can change the effective length of the pin and thus the clutch play. I know the 280 doesn't have this, not sure about the 250 - maybe the early ones?
I have worked on some 230s where that pin wasn't long enough to work the clutch, and I made longer ones from cap screws.