In Ubuntu 16.04 xenial I've installed unattended-upgrades about six months ago.
sudo apt-get install unattended-upgrades sudo dpkg-reconfigure --priority=low unattended-upgrades
after that time I ran in console:
apt-get update -y && apt-get upgrade -y
About 45 packages were totally upgraded.
I thought I should see about 5-10, but not about 45... This amout of upgrades surprised me a bit, as if, seemingly, unattended-upgrades "didn't do all the job".
Why unattended-upgrades upgraded so few packages, seemingly?