clarification (?)
Your LNB has two connectors.
If you apply 12 volts to either, it will set the LNB to Right hand polarization.
If you apply 18 volts to either, it will set the LNB to Left hand polarization.
...for that output.
Choosing between Vertical (12v) on your receiver and Horizontal (18 v), will allow you to choose between Right or Left twist, respectively.
Just as you pick between transponders that are V or H, choosing between RH and LH means you are on the same frequency but ignoring "the other signals".
Your LNB has two connectors.
If you apply 12 volts to either, it will set the LNB to Right hand polarization.
If you apply 18 volts to either, it will set the LNB to Left hand polarization.
...for that output.
Choosing between Vertical (12v) on your receiver and Horizontal (18 v), will allow you to choose between Right or Left twist, respectively.
Just as you pick between transponders that are V or H, choosing between RH and LH means you are on the same frequency but ignoring "the other signals".