Clarification regarding negative score

In the last contest(STARTERS 41) I saw that my rating dropped by -98 points, I want to know the reason behind that as I want to rule out the chance of codechef accidentally marking my honest submissions in plagiarism.
P.S.: I was able to solve only first 2 questions in last contest, if this info might help.

@ka_sh - so quick clarifications

  1. Our plagiarism checks usually complete over a 2 week period which includes our appeals phase. So yesterdays drop is definitely not due to plagiarism
  2. Rating Mechanism | CodeChef - ratings are a function of expected performance. So if others with a similar rating solved more problems → your rating can take a drop. For example - i solved 3 qs yesterday in div-3 and still had a 53 point drop. The system expected me to solve more given the other participants and hence the drop.

Thanks for clarification.