The draw works this way (going to use super simple numbers). There are 10 tags available for non-residents in the regular draw and 2 tags for the random. There are 20 guys who put in for the tag on a first choice ranging from 10 points to 0 points with 2 guys in each point ring. The tags will have been given out with all of the guys between 0-5 points not drawing. There are now 2 tags available for the remaining 10 guys who will literally be randomly selected.

Simplified, the guys with 6-10 points all drew and the guys with 0-5 points did not, but they each had a 1/5 chance of drawing the random tags. No one with a second or 3rd choice would draw this unit.

Now lets go to a unit where there are 100 tags and 20 non-residents who put in first choice. All draw. No randoms given out. 75 guys put in for 2nd choice. They draw and keep their points (assuming they did not draw their first choice) since you don't lose points for the 2nd choice. Now there are 10 guys who put in as a 3rd choice and 5/10 will draw, keeping their points.

Voila.