There is a Garmin bug: if you change target watt during a WO, it isnt the actual target watt, rather the first interval target watt and the problem it will be the active target as you log into this menu on Edge, make it simple you can see on this video:
Garmin try to prove this is beacuse 3rd party apps and solutions, but in this video this is a simple WO created in Connect and used only Vortex to control.
Garmin response : “it is not one that has been widely reported.”
If you have the same issue please report to Garmin maybe they will correct it sometime:
https://support.garmin.com/en-US/
Garmin topic: https://forums.garmin.com/sports-fitness/cycling/f/edge-530/282249/power-target-change