It 100% tells you that you have a notification waiting for you on the site. I get them sometimes after I've opened the site and navigated away. Seems like the browser's way of running in the background. Anyway, I get them on my PC, I use Tapatalk on the device, but it puts the dot on my shortcut icon for the site. Not sure if there is a way to stop it, I like it so I wouldn't want to. It's not harmful.