The hotspot display shows edit access (red) and read access (blue) to pages. It's a weighted average over the last 8 days, i.e. recent page accesses count more than older ones. FrontPage, RecentChanges, SearchPage and TestPage have been discounted from the table. Over rated pages can be scaled down, although none are at this current moment in time. Typically any edit will also have a corresponding read access, so there will never be pure read bars. The statistic is updated on demand from the log files every 20 minutes (1200 seconds). This is to discourage fiddling with it.