Lost 187 points in first game?!?
The site uses the Glicko rating system that includes a measure of rating uncertainty called the rating deviation (RD) value. Players with few games in a pool have a high RD value and will see larger rating changes after games. As you play more games your RD value will drop as will the magnitude of rating changes.
https://support.chess.com/en/articles/8566476-how-do-ratings-work-on-chess-com
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