The statistics are divided in three parts the first one is the global statistics:
When you arrive on this screen the statistics who are displayed are the global statistics for all the campaigns.
If you want to view the statistics of just one campaign you need to change the campaign in the dropdown on the top left corner of the page.
In the first part of the statistics you'll have these actual stats in percentage:
Successfully sent: the percentage of all the mails which are correctly sent
Open rate: The percentage of the mails which has been opened
Click rate: The percentage of the mail which the user has click in a link
Bounce rate: The percentage of mail that register a bounce
This graph show you through the time line all the number of times that your campaign was opened and clicked.
On the top right corner you can choose on which period you want to see statistics. If you click on the inputs a datepicker should open and then you can pick a date.
On the top left corner of the graph you can choose to watch data by month, day, or hour. And at the opposite you can hide one of the data (click, open) if you want.
You can hover the dot to get more information :