Odd behaviour of Software update.
I waited a bit before I wanted to restart through notifications, but it disappeared, then pushed the button on update in Appstore, said "Available Updates have changed" in a box, when I pushed the "Show Details" button I got what you see down below in a screen shot, did this a few times and each and every time I get one more entry in "Updates installed...."
I've had this bug every time i've tried to update Yosemite, really hope it won't follow through into the final release