I found that this page explains why your uptime is incorrect: https://www.winhelponline.com/blog/incorrect-up...
It says that with fast startup enabled, Windows keeps the uptime from the last shutdown.
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.