Hi,
A report like that is giving you information about the orders being taxed.
If you want to get the sum of taxes, you don't want to use a report.
Instead, go in the System>Taxes menu, click on the "manage tax rates" button at the top.
This will display the listing of tax rates, with one row per tax rate, and you'll have columns for the total taxed amount and the total amount of taxes collected. And you can use the filters of the listing, to select the order statuses and the period to take into account.