What causes a 50 point rating drop in a game?

My opponent started at 261 and I started the game at 278

I won with a rating of 286 so the typical 8 point increase occurred. What I don't understand is why my opponent dropped to a rating of 211 after losing the game.

Why the 50 point drop?

The PGN timestamp info is available for sharing and for some reason is doesn't display, Why?

The following is the our game..

[Event "Live Chess"]
[Site "Chess.com"]
[Date "2024.02.19"]
[White "Arun75007"]
[Black "Smile"]
[WhiteElo "211"]
[BlackElo "286"]
[TimeControl "120+1"]
[EndTime "18:48:05 PST"]
[Termination "Smile won by checkmate"]

• 1. e4 {[%timestamp 1]} 1... e5 {[%timestamp 4]}
• 2. Nf3 {[%timestamp 13]} 2...Nf6 {[%timestamp 12]}
• 3. Nxe5 {[%timestamp 17]} 3... Nc6 {[%timestamp 8]}
• 4. Nxc6 {[%timestamp 56]} 4... dxc6 {[%timestamp 10]}
• 5. e5 {[%timestamp 20]} 5...Ng4 {[%timestamp 31]}
• 6. Qe2 {[%timestamp 22]} 6... Bc5 {[%timestamp 52]}
• 7. e6 {[%timestamp 26]} 7... Bxf2+ {[%timestamp 73]}
• 8. Kd1 {[%timestamp 63]} 8...Bxe6 {[%timestamp 20]}
• 9. h3 {[%timestamp 33]} 9... Ne3+ {[%timestamp 230]}
• 10. Qxe3 {[%timestamp 116]} 10... Bxe3 {[%timestamp 29]}
• 11. Bd3 {[%timestamp 70]} 11... Bf2 {[%timestamp 145]}
• 12. Nc3 {[%timestamp 44]} 12... Qh4 {[%timestamp 94]}
• 13. b3 {[%timestamp 57]} 13... Qg3 {[%timestamp 256]}
• 14. Ne2 {[%timestamp 42]} 14... Qxg2 {[%timestamp 46]}
• 15. Nf4 {[%timestamp 33]} 15... Qxh1+ {[%timestamp 24]}
• 16. Bf1 {[%timestamp 66]} 16... Qxf1# {[%timestamp 22]} 0-1

Why does the PGN timestamp data above in yellow display this way? How do you interpret the yellow timestamp info?

Why does the timestamp above in yellow not display in the uploaded chess game?

His rating was unstable with a high RD, so he lost more rating than you won.

Thanks. What is RD ?

@4

RD is a rating dispersion calculated.

http://www.glicko.net/glicko/glicko2.pdf

This happened to me too. I think tygxc is right, but to explain it in more simple terms it might be because when you start playing for the first time a time control / variant on chess.com, you get more rating points to adjust to your actual rating quicker.

-@EnPassantAvalanche

Yeah, when you're new to the site or coming off a lengthy period of inactivity, you get big rating adjustments to help you quickly jump to a roughly accurate rating. When you've been actively playing for a while, you get smaller adjustments to fine-tune a rating that is probably already pretty close to accurate.

The Glicko link shared by @tygxc will go into more of the nerdy details.

Thanks y'all. It's been along time since I have experienced those rating adjustments. Unfortunately the points went the wrong direction.