Question about 'similar members' calculation

I'm wondering how the "Similar members based on your ratings" numbers are generated.

It just compares the ratings given to items, it only includes items you have both rated. e.g. if you have rated 10 items and given them all 7/10 and another person has rated 20 items and give them all 7/10 with 10 of them being ones you have rated them you will match 100%.

I intend to display the total number of items you have matched on so you can get a clearer idea of how close the match is.