It seems the update counts generally may not be populated correctly on initial login.
Under 19.04 I'm currently seeing these counts on initial login...
52 updates can be installed immediately. 0 of these updates are security updates.
...but then immediately after login...
sudo cat /var/lib/update-notifier/updates-available
66 updates can be installed immediately. 8 of these updates are security updates.
It seems the update counts generally may not be populated correctly on initial login.
Under 19.04 I'm currently seeing these counts on initial login...
52 updates can be installed immediately.
0 of these updates are security updates.
...but then immediately after login...
sudo cat /var/lib/ update- notifier/ updates- available
66 updates can be installed immediately.
8 of these updates are security updates.