I believe there is an error in that cad drawing.
If you compare the drop from the top of the bracket to panel (16 +6 mm) to the drop from the top to the hole centre (26mm) there is only +4mm drop.
Having quickly measured the drop from the panel to the bolt on my car I get +10-12mm. I think that the original drawing fails to take the metal thickness into account, add 6mm to 4mm gives you your 10mm drop.
Additionally, you have to take account of the thickness of the snorkel base plate that the bracket fits on top of, so the required drop will be + that, whatever it is...
I don't have a TF SNORKEL so can't measure that. Possibly another 2-3 mm..
Can someone measure that and I will amend the original drawing.