If you want to understand FargoRate, the FargoRate website has a FAQ page with lot of info.
Mike Page, who invented FargoRate, has posted some explanations here. He also has posted some videos on YouTube.
If you know chess ratings, FargoRate is a lot like that, but designed to be more accurate.
As mentioned above, if an 800 plays a 700, they will win twice as many games. If a 700 plays a 600, they will win twice as many games. If a 600 plays a 500, they will win twice as many games. That's on average. It is all based on the difference in ratings, and all those differences are 100 points. And if a an 800 plays a 500, that's three hundreds apart so the ratio of wins is 2*2*2 = 8 and the 800 will win 8 out of 9 games.
The FargoRate website also has a probability calculator where you can stick in the ratings and match length and see the chance for each player to win the match. If an 800 plays a 770 a race to 11, the better player will win 68.5% of the time, on average.