xert ftp vs. garmin ftp auto-calc?

hi and thanks in advance! based on same ride data from my garmin 820 + power (power 2 max) & hr - including a recent race - garmin’s built in app is calculating my FTP 15w higher than XERT. i haven’t done a standard FTP test for 3 months…is that the only way to reconcile these two FTP’s? appreciate all your work : )

Check to see if the FTP determination on the Garmin was established when your fitness was better. Note that seeing FTP fluctuate throughout the year is normal. If Garmin’s doesn’t make your value stale or show some decline over time, it can overestimate our real FTP in which case you’ll need to adjust.

will do, thanks!