I believe they use a benchmarking system. When a camera sets a new benchmark then it re-baselines the camera score database. If a camera sensor sets a new benchmark in all their metrics then I believe it will get a score of 100 and bump all the other cameras down to lower scores. I might be wrong, but I think that's how it works.
No that is not correct. The score is not limited to 100, cameras will score more than 100 and when they do it just means it is "better" than one that scored less. A difference of 5 points equals approximately 1/3 stop, so a camera scoring 102 is 1/3 stop "better" than one that scores 97.
But as they won't tell us how they equate those 5 points, or 1/3 stop, it makes it all pointless.