If your data seem inaccurate, you can try the Reimport Historical Data option, which is available in the app's Settings 7 days after the issue showed up.
Before doing that, I strongly suggest that you enable Apple Health app to track your activity continuously. You can do so by following these simple steps:
- Open Apple Health app and tap on Browse on the menu at the bottom of the screen.
- Tap on Activity, then Steps.
- Scroll down to the bottom of the new page that shows up and tap on Data Sources & Access.
- Tap on the toggle next to Stepz: it becomes green and successfully connects Stepz to Apple Health app.