If you are running several parent portals, each on a different domain and each having several portal aliases the SSO module will have to go through each alias and log the user in. This creates session cookie for each alias but if an alias doesn't resolve in DNS the loop will error out and break the process.
On installations with many portals and many aliases this will also mean a perceptible delay during the login process. And because no portal should actually respond to multiple aliases because of SEO duplicate content penalty, there is no point in running the login process on all of them.
That's where this SSO Options feature comes in - you can decide which aliases should be used for the Single Sign On process.
Simply un-check the boxes leaving only the aliases that you want to be processed.
