We have added three new heads up stats to the top of the lists screen so that you can see Total Prospects, Mailable Prospects, and % Mailable at a glance. Previously you could only see this on the lists overview page (showing all of your lists). We have also separated list information into three tabs, defaulting to the Prospects tab (e.g. list members).
You will start to see more and more heads up stats throughout the product. Pardot displays a ton of data and these call-outs help show you what is important at a glance.