Then as you may mechanically/manually move the blade from time to time, I wouldnt be setting a base value of 0% unless it is actually a fully closed 0% and then you re-adjust to the open idle position you need to achieve your idle speed.

If you set it to display 0% where it currently idles now, the blade could close further and you wouldnt realise as it would still display 0% although the voltage would change

Ultimately if everything is configured correctly around your closed/open values, it doesnt really matter though, but it's nice to have the displayed numbers mean something sensible to yourself and others.