You have the possibility to edit the sleep data tracked by your Go in the Withings App. To do so, perform the following steps: 

1. Open the Withings App.
2. Select a sleep item in your Timeline.
3. Tap on the three dots at the top right of the screen.
4. Select Edit my night.
5. Tap on Fell asleep at and/or Woke up at to update your sleep data.
   
6. Tap Save to confirm.