Software on this machine is up to date

[MR ZenWiz]

I expect to see this message whenever I have run the Software Updater.

However, since this morning around 9am, SU has popped up on the panel
(in background mode)  four or five times, with no other indication of
anything running, just that everything is up to date.

I checked the settings. The frequency is set to daily, with no
automatic updates at all - only automatic downloads (so I can update
faster when I want to do that).

I did enable the full Ubuntu Pro App updates and got quite a few I had
not applied but had  seen notices about here, but that's ok too.

Why would SU run at random times and show nothing useful as I described above?

Mark