This report shows how many Podcatchers were seen on your site. You can use this to check how many players you (should) have ready for visitors, and whether you might need more or fewer of them.
The top right graph “Trend” shows, somewhat unsurprisingly, the trend over the past while for the number of players. Podcatcher not seen for more than 3 months can generally be assumed to be lost or broken.
Lastly, the History table at the bottom is the verbose version of the graph. You can expand each of the categories to find and check on individual Podcatchers.