Hi
To credit progress towards your daily Exercise goal, the Activity app aims to identify activity that equals or exceeds the intensity of "a brisk walk". The definition of a brisk walk varies from person to person and depends upon your personal information.
Estimations of calories (credited towards your Move goal) also depend on your personal information.
To check that your personal information is accurate - and to update it over time:
- On your iPhone, in the Watch app, go to: My Watch tab > Health > Edit - tap and adjust items, then tap on Done.
During general daily wear, the Activity app relies on your arm motion (measured by the accelerometer) to track movement for the purpose of crediting progress towards daily goals. For the best results, allow the arm on which you are wearing your watch to swing naturally as you move around.
Calibrating your watch also helps to improve the accuracy of various estimations (including Exercise credit and calories) made by the Activity app and Workout app. More information and instructions for calibrating your watch are available via the link below.
More information:
Calibrating your Apple Watch for improved Workout and Activity accuracy - Apple Support
Use the Activity app on your Apple Watch - Apple Support