The question is why, if you measure at your subject (which you certainly should with a light two feet away from the subject), will the reading stil be correct if you set the cmaera up two miles from your subject.
The light seen by the camera has to travel those two miles after being reflected off the subject.
So before anyone else gives the same non-answer you gave, tell us why you can use the same setting you should use with the camera not two miles, but six feet from your subject.
Incident metering measures the light falling on the object, and that does not change no matter where the camera, or eye, is located. A face, for example, properly exposed at one meter, will remain properly exposed at two hundred meters, due to the fact that its image size decreases - proportionately.
A star many light years away is just as bright, per unit area, as it is from a distance of one meter.