It was a known issue within version 4.9.0. I've uploaded a hotfix just about a day ago (4.9.1).
Please update to that one, make sure to clear your browser cache, and try configuring that option again. It was a minor Javacript problem, where changing some parts of the the taxonomy term otpions did no effect.
If you like my products, don't forget to rate them on codecanyon :)