Hi,
I am on 13, but I assume the same works for 12. I'm guessing you tried deleting the Value Ordering property and then re-applying it from the Column Info window. Doing this, you will end up with the same list of values you just removed because they won't really be deleted until you apply the changes by pressing Ok. If you remove the Value Ordering property, press OK to close the Column Info window, and then go back in and re-apply the Value Ordering property, you should get an updated list with the new values included.
-- Cameron Willden