If licenses are activated already in some time in the past, then you should use the 363 days license, as the other one will expire sooner, both running license period from their activation time and date, no matter if they are installed and running in real time.
If not, then you can add one to another but just in case if both licenses are cumulative and one or both of them don't have a activation limit period (example : until 1.02.2015.)
Anyway, 100 companies 100 politics, you should find your answer at Emsisoft Support Team...