Marco, it seems to me the Jelco hasn't any graduate reference on the pillar for the VTA (I mean same printed or engraved notch), so how do you know the exact VTA you're setting (or re-setting)? are you using a bubble level or your own eyes?
The pillar, when loosened, simply goes up and down. I then nip it up when (yes, by eye) the arm looks bang on level with the record surface. Final adjustment though is always by ear, where I will then fiddle around for sometime making minute adjustments, before getting the VTA spot on, sonically, using various test records.

There's not much point in having engraved notches on the arm pillar, or whatever, if the 'sweet spot', for optimal VTA, falls somewhere in between!

Marco.