I've seen this before too with many other creatures, and I'm pretty sure that it is just a glitch that involves the hit damage appearing where it's not supposed to because it can't fit above the creatures head. I've also seen hit damage appear so far above creatures heads that you can't see how much you just did. Hope this problem gets fixed soon even though it isn't really glitching the game at all. Because of this I missed seeing myself do one million damage and getting the 1 in a million badge . Hope this helped!
. Hope this helped!