The scoring system is quite simple (honestly!) and is designed to encourage everyone to attain their best possible time. In each race, the overall winner will score 1000 points. All other results are then calculated with reference to this winning time as follows:
Winning Time/Your Time * 1000
So, if the winning time is 4 hours and your time is 5 hours then you will score 4/5 * 1000 or 800 points.
The difference between this system and a "placings" system which awards, say, 100 points to first place and 95 points to second place etc is that you are encouraged to race to the line. If your time is seconds behind the person in front, the point difference will be minimal.
So, the maximum possible score for the overall series is 4000 points. In the unlikely event that more than one person scores a maximum, the overall championship will be determined by taking the next best scores (above 4 races)