If you look at that stat in combination with the other table, it means your above average scores aren't usually much above average (I’ve got the raw data if you really want specifics)

You’ve had 3 really good GWs where you’d expect to win
A further 6 decent GWs where you’ve got a chance of winning
And 11 GWs where you’ve underperformed and would be lucky to win

!BEER