Why does calories burned during an exercise change depending upon how it's logged

[BarnOwl_18]

Hi I'm just got a Versa 2 but I suspect that this is a more general fitbit question than specific to the versa watches. I have my fitbit data synced to my weight watchers app and I've noticed that if I remember to track an exercise whilst I'm doing it I apparently burn significantly more calories than if I add it to the app after I've finished it. For example I did a yoga class on Sunday and was running late so I didn't get a chance to start my watch before class and apparently I I burned 398 calories in the class. I did exactly the same class on Monday but had time to start my watch before the class started and I burnt 1,082 calories. I'd imagine that in both cases the recorded data is exactly the same as both show similar heart rate graphs and similar maximum and average heart rates. I'm wondering why the calories burnt then is so different. This is also reflected in the exercise points that I accumulate in the weight watchers app, Sundays yoga session gave me 7 points and Mondays 37!

[JohnnyRow]

On the day you didn't start the exercise session on your watch before, you didn't specify that you manually logged the class afterward.
But if you did do so, manually logging a workout overwrites the actual data that was recorded with an estimate from the parameters you  used in logging it.