The Lucene hit score is not supposed to be interpreted strictly as a percentage, since the score can be any real number. Especially since
XWIKI-6217, this has become more apparent, with percentages sometimes going over 2000%.
Since the hit score is rather technical, it shouldn't be displayed. A quick fix of the problem is to cap it at 100%, since it doesn't matter how much above a perfect hit it is. Still, I think that the score is not a relevant piece of information, and it rather tends to distract from the results themselves. What matters is the order of the hits. It is possible for a document to be the right thing that the user is looking for, but to have a low score which discourages them from opening the document.