The Negative CMT score

When I look at different user profiles I sometimes see a negative CMT score. What does this mean?? EX. Kimberlite is at -743.

They been inactive for more than 90 days
on the score board their score stops at 0
so if they ever come back & enter more bills their score will be positive again.. & for the scoreboard they would start at 0

I hope that doesn't happen to me. Thanks for the quick reply Lord_Comedy.