Just so others can refer to the same page, as well: http://brokevw.com/releasearm.html
Yes, all adjustment is done at the trans end of the cable. Once adjusted with the free-play at 12mm (measured at the top beneath the adjustment per the drawing), you should be in good shape so long as there are no other issues (ie. pedal cluster, bent finger, etc., per Broke's list of culprits). When I did mine several years ago (new clutch kit, seals, throw-out bearing, cable, etc.) for the first time, I simply tightened the adjustment to the point of having the lever at 9 o'clock (on the verge of beginning its release action), then backed it off to get the free-play. In all honesty, I "eyeballed" mine (I think I once measured it at 10mm, so it was close... lol) and it has worked well ever since. You will know in short order if the adjustment is off, for it will either not release at all (too much free-play... A lot, in fact...) or slippage will occur (no freeplay at all, thus not fully engaging the clutch). Those are obviously extremes at both ends of the spectrum... As for how many mm the end of the lever travels below the 9 o'clock position, I haven't a clue, since I've never measured it there (your principle theory is correct, though, and the measurement is probably close, if not the same). Hope that helps out.