These are presented on a "Boston Matrix", which can be confusing if you haven't seen one before. It's actually quite simple.
Each quarter of the chart shows the combination of good / bad bidding or card play:
- Bottom left - boards where both the bidding and the card play were worse than the double dummy
- Bottom right - boards where the bidding was worse than double dummy but the card play was good or better
- Top left - boards where the bidding was as good or better than double dummy but the card play was worse
- Top right - boards where both your bidding and card player were as good or better than doubel dummy
Board numbers that are shown in white are the boards where you were dummy (so not responsible for the card play!)
The chart for the top third shows what percentage of boards fall into each of those categories for the players who were ranked in the top third for this game. This example shows a typical result for a matchpoint-scored club game. It shows that winning players tend to play the cards very well, even if their bidding isn't necessarily very close to the double dummy. Here. 55.56% of boards fall into the 'bad bidding' category, whereas only 17.78% of boards are classed as 'bad play'.