Initially I participated in Div 2 of July Challenge with a rating of 1710.During the Long Challenge there was a bug because of which the results of June LunchTime were deleted and I was promoted back to Div 1.I made submissions in Div 1.Later the bug was corrected and I participated in Div 2 for the rest of the Challenge.
Div 1: Rating change: -175
Div 2: Rating change: +136
Ended up with a rating of 1671 (-39).
Yes, there is no issue with that. You can look at Rating Mechanism | CodeChef to know more about the various factors which go into this calculation - it won’t always be intuitive.