On the tab "The Actual sort order" the Addressing for Index() is inclusive of all Dimensions in the view so the Index is overall. The Sort is applied overall, ascending and therefore starts from smallest to highest sales value across all of the values in the view. Without the restart per Region the setup that you have defined will include all Regions.
I suggest also reviewing the table calculations with the Beta version of 10.0 or with the new version when it is released because the new Table Calculation interface does a nice job of highlighting the measures involved. In version 10, the configuration of the same table calculation is easier to see as changes are made.