I honestly can't think of anything that the door number could be related to, I believe it's random. The most likely theory is that it's your target finishing position to not lose DR or whatever, but then again, how do you test this?
I'm going to put an example here. Say you're an A-class driver with 35k DR exactly so as to not fool around with decimals and such. This is the starting grid for, for the sake of simplicity, a daily race at Tsukuba Circuit in the early morning where there aren't many people playing:
-1: Driver 1 (A-class, 37k DR), door number 1
-2: Driver 2 (A-class, 36k DR), door number 2
-3: You (A-class, 35k DR), door number 3
-4: Driver 4 (B-class, 27k DR), door number 4
-5: Driver 5 (B-class, 25k DR), door number 5
-6: Driver 6 (B-class, 20k DR), door number 6
If we go by the "door number related to finishing position" then, this could make some sense, in this grid. You should finish ahead of the people with way less DR than you. But, now, what if we switch this all around? Say, Driver 6 and 5 are alt accounts (just to put it into perspective) from two aliens and they have locked out the front row. Then, Driver 1 had a pretty miserable qualifying lap, and dropped some places. This would be the new grid:
-1: Driver 6 (B-class, 20k DR), door number 6
-2: Driver 5 (B-class, 25k DR), door number 5
-3: Driver 2 (A-class, 36k DR), door number 2
-4: You (A-class, 35k DR), door number 3
-5: Driver 1 (A-class, 37k DR), door number 1
-6: Driver 4 (B-class, 27k DR), door number 4
I have not changed the door numbers since, technically, they should be related to DR according to the others around you, right? Well... here's where the system kind of falls apart?
While Drivers 6 and 5 don't see a whole lot of change (and to some extent also Driver 4), the door numbers for Drivers 1, 2, and 3, are quite irrelevant in this scenario. Look at it this way; to offset possible DR loss, all of them HAVE to get past Drivers 6 and 5, because since they have such a high ammount of DR difference, they will lose a lot more than what they will gain by beating themselves and Driver 4, who is at the back. In fact, Driver 1 should finish first as he has the most DR to lose.
Now I'm not sure if in this situation the door numbers would change or if they vary according to starting position or some weird algorithm, but this is a what-if scenario if the same drivers with the same DR ammounts meet each other in two separate Sport races.
Wish PD just... you know... let us know? This shouldn't be rocket science and yet it is...
