How does the rating change works at Codechef?

Okay, I recently gave a contest.
My friend got a rank around 310 in div2.
I got a rank of around 320 in div2 in the same contest.
His rating changed like this. => 1774-> 1801
My rating changed like this. => 1764 → 1812.
“I” got better +ve delta even though “HE” got better rank.
Why is that?

I believe it’s because I have given fewer contests(only 7), whereas he has around 70 contests. Is that the reason?
Can anyone clarify this?

And also, is it the same case in Codeforces and Leetcode?

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