Well, because your PR guy doesn't have time to ask ALL your fans every time, the fan survey shows the feelings of just a small group of them. This time the group he asked was a bit more negative, but probably still gave you a 4.24 star rating for your perfomance this season. This is shown (obviously) as a 4 star rating where your 5 star rating was somewhere between 4.76 and 5.00. Therefore the differance could be just slightly over half a star and in the overall rating that wasn't enough to make your overall rating drop...
BTW nice job! :D