The Campaign Trends tab is where you can compare the performance of your campaigns over time. The number on the vertical axis of the graph shows how many times the campaign was either opened, unopened, subscribed to, or bounced (this will depend on the campaign category you choose from the dropdown box). You can choose the campaign category and the email category by selecting a category in the “Campaign Category” and “Email Category” in the drop-down menus located above the graph. The horizontal axis of the graph represents the campaign emailed. The Legend will explain which email campaign the point on the axis corresponds to.