Technically, that is not HIIT. I mean, its all relative depending on the condition of the person, but my question is this. While running at 9 mph, are you pushing yourself to the absolute max? HIIT is all about going to your bodys outer limit, you should finish and barely be able to walk. I can run at 9 mph for miles, so for me, an all out sprint at 12-14 mph would be my HIIT level...
Make sure you are pushing to your limit.