OK, here is how it works:

Each person gets 1 point for a win, 1/2 point for a tie, and 0 points for a lose. Both you and dexter got 5 wins, so you each got 5 points. That is where the S-B comes into play.

First lets take dexter: He won against player 2, 4, 5, 6, & 7. Now you add how many points each of those players have. Player 2 had 5 points. Player 4 had 4 pointst, #5 had 3, #6 had 1, and #7 had 0. Add those up and you get the S-B (which is 13)

For you, you won against player #3, #4, #5, #6, #7. So you add those points up. (3+4+3+1+0 = 11)

I hope I explained that well enough! :-)