Interesting! The Ring controls digital displays look more like free labels than numeric controls. This applies to text rings as well as pict rings.
When you customize a knob, gauge, or slider, the digital display is the actual numeric part which can be repalced by other types of numeric controls. The knob or slider is just an image. When you customize a ring, all the pieces seem to be images. No numerical part is there.
Someone from NI will need to let us know what is going on.