If the flat value difference on the bed is less than 2mm, it meets the factory standard of Creality.
The cause of deformed bed and how to adjust to get better printing effect can be seen in the video below.
https://www.youtube.com/watch?v=8PEsPLDxt-c
https://www.youtube.com/watch?v=CsIAJgCAxFM
https://wiki.creality.com/en/k1-flagship-series/k1-max/troubleshooting/leveling-trouble-shooting