Modify positioning formula

[jingwuluo]

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. Run yarn in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Run yarn start in the example folder to test your changes.
5. Ensure the test suite passes (yarn test). It uses the example
6. Update the readme if needed or the documentation
7. Update the typescript definition is needed
8. Make sure your code lints (yarn lint --fix).

Learn more about contributing here

[fkhadra]

Hey @jingwuluo ,

Can you describe what your PR bring? I'm failing to understand. Thanks a lot