CTC-5 Westcott restoration

[SwizzyMan]

Not quite satisfied with the color temperature. While trying to do a proper temperature setup I ran into some difficulties. The manual says to turn the green and blue background controls 30% up from being at counter clockwise. And to turn the contrast control to the halfway position. I know what all this means but how could I tell where 30% is on the screen controls and where halfway on the contrast control is?