Transunion scoring makes no sence.

I cant understand, how can you have a credit rating of average the one day, end of the month, next day beginning of the month, my score has dropped with 17 points and there is no diffrence in the details. How does Transunion work out the scoring, because it seems that even with no negative effects, a normal person can not get there rating up because of the way Transunion is configuration of scoring.