This clearly shows how a reduced off set increases trail (never mind my reasons why for now) using 'normal' reduced off set yokes, ie the fork centres move closer to the stem centre. The nichols items move the stem centre back or forth relative to the frame cenre using the off set tube.
This pic ducati dad put up shows the setup with 'minimum' offset - distance between fork clamp centres and 'steering bearing' centre - if you turn either of the eccentrics round 180 degrees it will increase that distance therefore increasing offset
@Tobytyke At the risk of laboring the point. The opposite (180 degrees around) of how part 6 is shown below? The lobe pointing away from the bike?
photo is worth a thousand words? hope this 30mm Off Set Triples. helps Exccentric spindle alloy part and steel inner stem turn together, you can now see how the inner and outer spindles can be set to shift offset