According to our IT team, following are the steps needed to clear these push notifications:
1) Block the notification settings for https://samsonsociety.com/ in the browser settings.
2) Clear the browser cache.
3) Restart the browser.
4) Now if you want, you can allow the notifications again and should not see any further spam notifications in the browser.
Please try following the above steps and let us know if the issue persists.