Xiaomi Realme Watch S Mode D'emploi page 6

Tips:
 Before binding, make sure your phone has Bluetooth turned on,
and that your phone is properly connected to the Watch.
 If you fail to find the Watch when trying to add it, or are unable to
connect to it when using it, try restoring the Watch to factory
settings, and then add it again in the APP.
Binding
successful
04. Wearing
Wear the Watch about one finger away from your carpal bones,
and adjust the strap to ensure that the Watch is tight enough for
the heart rate sensor to properly collect data.
Tips:
 Your heart rate monitoring data may be inaccurate if you wear the
Watch too loosely.
Binding
failed