Unable to save Post Page Options

After modifying the label text to "Label："
I could not for the life of me change the double byte ： back to single byte :.
It just would not save!!

As soon as I save, then I would open the options again, and it went back to what I had previously.

If anyone's having trouble like me with the Blogger post options,

located at
Layout > Page Elements > Blog Posts > Post Page Options

just delete whatever you had in there and save, then reopen and the option will go back to default.
Then try going from there.

It really is not very intuitive since there's no "default" button.