I'm not jonas, but if this jam works like others I've been in I might know how it works.
The median was 10 ratings, and it reduces your score if you have less than the median, but doesn't change it if you have more than median. So you would only get your score reduced if you have less than 10.
That's why I wouldn't buy into the whole getting your game rated as much as possible craze, unless it is solely for the purpose of getting as much feedback as possible. In every single big jam I've joined (except one), the winner has been a game with just barely enough ratings to avoid getting their score adjusted. So yeah, essentially getting less but more quality ratings does lead to a higher score, because there's less of a chance for more people to see it and rate it poorly.
Hope this answered some of your questions, but then again the scoring system doesn't really matter so I wouldn't but too much stake in it, it's more about if you got quality feedback and learned from the jam