What do I put for "Blog to backup" when I want the whole network backed up?

Hi,

I have a multi-site setup. Our main blog is for our company (shift-forwarddesign.com), and the other two are individual portfolio websites (james.shift-forwarddesign.com, olivia.shift-forwarddesign.com). I am trying to setup a snapshot for the entire network. What do I put in for "Blog to Backup" to create a snapshot for the entire network? It seems to only allow one blog.

Would entering shift-forwarddesign.com (the main blog) also backup james.shift-forwarddesign.com and olivia.shift-forwarddesign.com?