Leader plus 1 at the scoring loop unless it's the checkered...leader across the scoring line (the front of the flagstand, not the scoring loop on the last lap) ends the race, then it split scores back to the last lap minus the caution cars for cars that didn't cross the scoring line. The only way to do it any different is to have multiple loops like NASCAR does - then there would be a question of where the multiple loops are and why they are different at different places.

You have to draw the line at some point that's the same for everybody.

I prefer that method to "every single car even the caution cars" or you go back, or "every single car minus the caution cars" - all ways that I've seen it done...