OA2 Spaces Groups Inheritance

I created a Private, top-level Space (no parents) and I created a Group. I assigned the group to the space so that members of the Group would have access to the Space. When I view the Space via the Edit button, I see that the Space is now a Child of the Group?

What's happening here and how does this affect permissions that I've set?

Does anyone know how I need to set up both the Group and the Space so that Space permissions override group permissions?

Thanks,
~Dogtag