How does Codechef calculates its ratings

After being wrongfully accused of plagiarism in the last contest, I worked hard in today’s competition and secured a rank of 257, but my rating only increased by 44 points. How does CodeChef calculate its ratings? I’ve noticed people with ranks between 800 and 1500 in Div 4 gaining around 100 points, which doesn’t seem logical.

@anon16326798

You can read about rating system here Elo-MMR ratings go live on CodeChef!