According to the tutorial, morality weight is inversely related to the number. In other words, the larger the number, the smaller the impact. Unfortunately, I cannot state this with conviction as I see conflicting evidence in the event files. Some events that should (IMHO anyways) have a large impact have large numbers, supporting Verenti's assumption, yet other events that should have a major impact have low numbers. So go figure.
The official word is, however, what I stated above.