ClarkSteveB --this is from The Learning Center section - Hubpage Exclusives:
Note that after selecting an Exclusive title, you still have the option to change it (until you enter the HubTool). That said, it will no longer count as an Exclusive once you have altered it. You will be able to tell whether a title is an Exclusive or not by the color of the title text box. Yellow outlines indicate Exclusives; blue outlines indicate normal titles.
Once you have entered the HubTool, you will not be able to change your title; the Hub has been irreversibly declared to be an Exclusive.