What do beard trimmer comb settings mean?

Most men’s beard trimmers come with a detachable comb that can be set to a series of distances from the clipper blades by means of a numbered thumb-wheel. Settings on my Remington Titanium MB-35 range from 1–9 and I think that is pretty standard for trimmers.

Do these numbers relate to a specific distance from the blades that is standardized across shavers and clippers, or must you just experiment or use a gauge to actually measure what each setting gives you in hair length?