Hello !
see these two graphs and the rank in bayan warm up (in graph) and the rank in contest standing !!
The rank of mamadak in graph is 255 but his/her rank in contest's standing is 1990 !!
The rank of codefork in both graph and contest's standing is 1661 !!
Note : codefork ranking is better than mamadak but mamadak got +264 but codefork got -16
That's a very good question. I have no clue why that's the case. Not sure why you got so many downvotes either.
For those who didn't understand what Tparsa meant, mamadak is ranked 1990 in Bayan Warm Up. However his profile says rank 255 and his rating increased significantly. So if someone can explain this confusion, that would be great.
I personally have no idea what could cause that.
P.S.
Well, I did some research while writing this comment and I found this blog which describes him cheating (not the first time I've seen accusations of him being a cheater). So my best guess is that his solution was skipped due to cheating, and therefore his ranking changed. However rating changes were already done and to recalculate them you'd have to recalculate everybody's rating, so his rating stayed high.
P.S.S.
I tried to make the links relative so you don't get logged out and transferred between codeforces.ru and codeforces.com :)