How does Garmin Connect model ones FTP?


On my Fenix 6x I set physiological metrics -> auto detection -> FTP to "on", so I assume Garmin has some algorithm to model my FTP, or is that wrong?

I tried to set my FTP to "140" on the watch, which is way to low. With that I expected that after a few workouts on my power meter equipped bike that Garmin would correct my FTP value. But until now that didn´t happen.

So does Garmin connect has an FTP modeler integrated which could estimate the users FTP? Or would I need to do a real FTP test?