Different Admin page and self-assembled LCP metric values

I’m collecting performance metrics and saving them to my db using this guide - Admin, installation, and OAuth performance . But LCP metrics that I’ve collected are not the same as I see on “Admin performance” page for specific period of time.
For example: on 24th December n “Admin performance” page LCP is 4.58, but collected metrics shows LCP is 3.11. Could you please explain why they can be different?