I'm gonna try this. But it's on an assumption.
I have reason to believe that the Battle Spot follows an ELO system of rating. This is the same mannerism of rating in chess. All players start with a bonus rating of 1500 and the number of wins they get under their belt, the higher this rating goes. Likewise the more losses they incur, the lower the rating dips. To learn more, see here.
The thing about ELO though, is that it has no lowest or highest point. Heck it can even go negative, but it will be displayed as zero. Henceforth, I lead to the conclusion that the ratings have no lowest or highest points.
Hope I helped!