Adding to Jürgen's reply and copying what I replied on your parallel message on Badges/Points on blog not alloted
Sometimes points are removed when an action is undone. Unfortunately, the entries remain on the history list.
From SCN Gamification Known Issues
The history does not show negative points when content is removed, or actions are reverted (ENHANCEMENT)
Result: It is not clear why your lifetime point level goes down. Moderators cannot check that they indeed removed points for a user.