If you notice that your realtime update-enabled Google Sheet contains two rows for each newly-created Jira issue, it may be because another third-party add-on is editing issues immediately after they are created. The solution to this problem is to disable the "Issue Created" webhook in the Google Sheets Integration Configuration screen:
Disable "Created" webhook:
For more information on webhook configuration, please see the Webhooks Configuration section of the Jira Add-On Configuration page.