Whenever AppCenter shows that there are updates, I notice three things happen:

1. The icon in Slingshot menu shows the update count.
2. The icon for AppCenter temporarily stickies on the dock with the update count shown.
3. There is a notification which can be dismissed at will.

I usually prefer to do my updates via the terminal so I can see what is changing. However, I've noticed that the AppCenter icon still sits in my dock and shows an update count, and so does the icon in Slingshot.

The intended behaviour would be that once the updates are done, the icon would leave the dock, and the counter on the Slingshot icon would go back to nil.

I have tried updating my package list again using apt from the terminal (which tells me all my packages are up to date), but the icons still show updates.