The group select box is a multi-selection options box.
Please see the attached screen shot.
You can select off (ctrl + click) the extensions you want to be included in the group and simply 'save'.
The highlighted extensions are the included extensions within that group.
We will look into making this more obvious/clear.
Let me know how this works out for you - thanks!
Screen Shot 2013-09-30 at 12.54.55 PM.jpg
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