The Financial Summary is an estimated snapshot and it is created when you upload a new invoice so it relates to that individual Invoice. You can view all of your Financial Summary reports from the Reports menu on the left.
In the detailed view (shown blow), you can see the Total Invoice Value (inc. VAT) as well as the Total Net Value and all outgoing fees that might be related to this invoice for tax purposes. These are estimated based on the information you have provided when you create the Invoice Reminder.
Lastly, you will see the final earnings tally figure at the bottom which is the Total Invoice Value minus the Tax Deductions.
Some of this data is also used on the Dashboard to generate the information on the panels.