As I explained to you, points are decreasing due to violation of guidelines by you.
Actually points are not deducted.
Whole posting proccess wroks like this- Whenever any person posts answer it gets on hold for approval and instantly system assign some points for that answer, then during approval of answers by Moderator it is checked if answer is according to all guidelines, if answers are according to guidelines it gets approved otherwise get deleted as a result point assign for that answer is taken back automatically.