当我看到FB桌面的消息时，FB messenger如何从iOS应用中移除推送通知?

Whenever I get a notification about a message on my iPhone from Facebook and I reply to that message from Facebook website, that push notification goes away from my iPhone home screen. How is Facebook doing that? I know push notification don't have delivery confirmation mechanism in iOS. Here in this scenario Facebook knows I have read the message so are they pushing something to their app to remove notification? Even if they're sending a message to their app that I have read this message how is app removing that notification when I don't have background app refresh enabled for FB messenger or FB iOS app.Whenever I get a notification about a message o