10+ page thread about Soccer Rankings
right over here, so probably shouldn't rehash it all here. But quickly - teams start with a generic rating by age group. As rated teams play each other and their scores are loaded electronically, their relative ratings are compared. If their actual results are better than expected results, their rating goes up a smidge. If their actual results are worse than expected results, their rating goes down a smidge. Exactly how much is complex, as it depends on the results of all of the other interdependent games that all of their opponents (and all of their opponents) ((and all of their opponents)) complete. A team gets a valid rating after having ~6 to 10 games against other rated teams within the past 7 months. Newer games count more than older games, and once games are 6+ months old, they count very little if at all to affect a team's rating. The ratings can be compared as goal differences. For example, a team rated 47 would be expected to beat a team rated 45 by two goals. A higher rated team in the US will beat a lower rated team 83% of the time. For a number of viewers of this board, a higher rated team will beat a lower rated team that they are following 75% of the time, as things get a little more variable when you're at the pointy end (top 100 teams nationally).
A club rating is calculated by taking the rating of the club's top team from U11 through U17, and averaging them. The club needs to have at least 5 teams in those 7 age groups to be calculated; if one or two teams are missing a team the missed age group gets a generic "30" to still have 7 ratings to average. In this case, it's showing that Surf is the 2nd strongest club (girls) in the nation, and on average their top team would beat the top team of Koge , the 3rd strongest club, by 0.3 goals. Clearly that is quite close. For some age groups, Koge is stronger, but for more age groups, Surf is stronger.