Question:

Why doesn't the first received message notification bubble disappear, while other bubbles disappear?

Answer:

Message notification bubbles are designed to display up to 10 messages. When an 11th message is received, the oldest (firstly confirmed) bubble is deleted to make space for the new one. This means that the first received message's bubble may not be deleted.

Terms:

Message notification bubble - A visual indicator showing that a new message has been received.

Display - To show or present information on a screen.

Up to - Maximum limit or extent.

Confirmed - Verified or acknowledged by the user.

Delete - To remove or erase data or information.

Make space - Create room for something new.

New message - An incoming message that hasn't been viewed or processed yet.