You can use the CV Trim option in the editor. Just plug in your QuNexus to the computer, open up the editor, go up to the Hardware menu and select CV Trims.
In the window that pops up change the Trim number box (for 1V/octave). It's pretty much just a multiplier, so raise it a bit to widen the space between notes or lower it to reduce the space between notes.
There is also offset, which just adds or subtracts. These are pretty much the only options for CV calibration.
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