Rating fluctuations after contest.

Umm, @admin, could you please explain why my rating first rose by some 50 points, then fell by more than 180 points even though I had attended no contests in between. The first increase was after July Cook-Off 17. However the subsequent decrease is what is confusing me. Is this some kind of a bug? or else, could you please explain to me what happened?

P.S - had solved 3 problems in COOK-OFF so I dont think that the reating should fall by so much even as a result of the cookoff.

This question has already been answered here: https://discuss.codechef.com/questions/106651/july-cook-off-ratings-suddenly-decreased

They have tried to experiment some stuff because of the problem with partial point system and it reflected publicly.