I think this is due to the way rating is calculated. It's an ELO-like system, so for every user something like his expected place is calculated and then if he does better than expected, his rating increases. Now ElemeNtLz has higher rating, so his expected place is higher, so when he gets second place he does better than the expected place but not MUCH better. While as far as I remember, when a user is competing for a first time his expected place is the participants/2-th place, so yyfkiller3 did MUCH better than his expected place. Therefore according to the ELO-like system he has much higher improvement.

I'm not saying it's fair though, that's a matter of opinion. I remember sometime ago an unrated guy participated in memsql cup round 2 as his first round and he got a little bit behind the half, and got his rating decreased. While blue competitors in the lower half got rating increase, simply because in the competition there were a lot of red/orange coders so saying an unrated guy is expected to be placed at position participants/2 turned out to be unfair, but that's how the system works.

This is a top secret code that codeforces uses to calculate the rating.

class RatingCalculator {
	Random random;
	int numberOfParticipants;
	public RatingCalculator(int n) {
		random = new Random();
		Thread.sleep(random.nextInt(22831337));
		numberOfParticipants = n;
	}
	
	public int calculateNewRating(int oldRating, int place) {
		double p = 0.5 - (place - 0.5) / numberOfParticipants;
		return oldRating + (int) (322 * (0.7 * p + 0.3 * random.nextGaussian()));
	}
}

I had this same issue with codeforces round #FF. I placed 120th officially and my rating change was 1522 -> 1689. A couple of other people who placed below me had either higher or lower ratings and they still became candidate master (rating >= 1700). Just my opinion that this rating system is a little unfair to those with not too high and not too low ratings.

I think rating changes also depend on the number of participated contest (something similar to Hackerrank 's system).

RATING it is.