The Site dashboard gives you an overview of your whole website with general system metrics and also notifications of important updates from b2evolution.net.
This shows how much data is in your database, all collections aggregated.
The circles will appear full when the count reaches 100,000. This does not mean that b2evolution is limited at 100,000 - it merely means that you should consider using a dedicated server when you reach this point.
Updates from b2evolution.net
This will tell you if a new version of b2evolution is available to download and it will also recommend if you should upgrade your current installation.
The alert will be displayed in red when there are critical security updates available.
This panel allows you to quickly create new collections by using existing collections as templates or models.