These 12 months run from the activation of the first user! The term is counted from the start of the main user.
And - last year I had the problem that I only entered the new licence 2 days before it expired, and the message "Licence expired" popped up at my parents' house. And it probably stayed there for another three days... Everything is better this year - I bought a new annual licence and have already entered it! Now it says runtime until October 2021.