What length in pixels does a Wings3D unit of measurement equate to?

[frostic]

ok so I don't know if I'm doing this right but I will explain what I'm doing and hope someone will know why I'm getting the wrong size holes.

NOTE: cura auto scaling is turned off

when I create a cylinder with a radius of 15 by setting settings like in my image below
then i use boolean to cut this out of a cube all looks good in wings but after export to stl and import to cura using the stl plugin listed above setting it to 1 STL unit
my hole that was made using 15 of the scale prints as a 30mm hole instead of 15.
same as if i make a cylinder size 3 it prints at 6mm i'm guessing that when creating a cylinder 15 does not mean 15mm?

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odd the little box above this text is my image but it only shows if you click the little box i don't get why its not showing lol let me try another image in jpg below

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