Almost every time I premove, I lose at least 1-2 seconds, and sometimes lose 20 seconds
Premoves will take a minimum of 0.1 seconds. However, if you're experiencing high lag and/or disconnects, they can take longer.
https://support.chess.com/en/articles/8584209-how-do-i-fix-my-disconnect-lag-issues
https://support.chess.com/en/articles/8652402-how-can-i-optimize-my-online-chess-performance
Almost every time I premove, I lose at least 1-2 seconds, and sometimes lose 20 seconds