GeoIP Alias Question

[spetrillo]

When setting up my alias I notice two boxes that can be checked but what do each do. Which is to block and which is to allow?

[cookiemonster]

It seems from mine that the left box gets a tick when one or more countries are selected.
The right hand side box remains unticked.
If you then tick the right box, it clears the selection.

The block or allow actions are on the rule that you need to create after having the alias created.