I just got my first Apple Watch and I notice the activity app tells me I've completed various goals at very strange times. I'm not particularly active. I exercise 15-20 minutes 3 times a week. But, I'll be sitting on my sofa late in the evening and I'll get up to get something from the refrigerator and my watch will tell me "Congratulations! You reached your goal for X!". I'll turn over in bed and it will tell me "Congrats, you reach your goal for Y!"
This happens regularly that in periods of doing almost nothing the Activity app tell me I reach my goal.
That got me thinking how does it actually work? How does it know me lifting food to my mouth is different than me living a weight?
Is there any info on how accurate Apple Watch is knowing what the user is doing?