alexlee, I think it means that if you and one other player get, say, 5 points each, the S-B points will come into consideration.
So the players you beat, THEIR points will be added up (the games they won) and this is the S-B for you.
In other words, if you beat good players and they won most of their other games, you'll have the higher S-B than the other player if the people they beat didn't do so good overall.
Its like a ratings system, so the actual game type doesn't matter.
Does all that make sense?!!