How do you change a Dimension's 'Element Class' from "Primary" back to "Dimension"

I have accidently changed some of my dimension's Element Class from "Dimension" to "Primary" and I am unable to change them back. I would like to know where to find the settings for this and possibly Key-In command or Configuration Setting.

Element Type: Dimension, Element Class: PrimaryElement Type: Dimension, Element Class: Dimension