There are 2 use cases for the Reset button:
to remove old migrations that are no longer needed and combine all migrations into one file (faster, better, prettier);
to reset the database by deleting it completely and creating it again.
To reset your project, please go to your project's settings. Then go to the Settings tab and click the Reset button.
With this action, you will delete the database with your data and migration history, keeping only the last state. Your code will then be pushed to the GitHub, if it (the GitHub) exists.