Distance was designed to try and suppress highs in sound, as if the sound was coming from a great distance… BUT, not through just rolling off treble.
Through slew restricting. Not even equalization at all.
This is so unusual an approach that it won’t work on many sounds, not by itself. If you take something upfront and normal and try to make it ‘distant’ it just won’t work. The trick is to take something that’s meant to be distant, like a reverb return, and put Distance on that. Match what’s there with an appropriate Distance setting to put the finishing touches on the sound.
Ignore the ‘miles’ part, think of it as just a slider that can be adjusted to place a distant element in its correct depth. Distance can’t really impose upon a sound, a specific distance. What it CAN do is take a sound that’s meant to be coming from a distance, be it ever so far… and make that really convincing in a mix.