In game Steam notifications gone haywire ?

[Ghiblifrost]

ISSUE
The in-game overlay displayed a bunch of outdated notifications (36 in my case) about completed downloads as if catching up to something, including the game I had just launched.

OS
Windows 10

STEPS
Download a bunch of games or software, including Ride 4
Launch Ride 4 (was this one in my case, didn't do it on Mirror's Edge)

RESULTS
All the recently finished downloads pop up one by one even after being removed from the completed queue.

EXPECTED
Only the downloads finished while playing the game should be notified.