Certainly nothing important and doesn't bother me at all but never-the-less an interesting little insect.
Initially you get 1 more concurrent mission than your number of fire stations. That worked fine till about 50 or 60 fire stations. After that I only got the same number of missions as my number of fire stations built. But when I built my 100th fire station I got up to 101 missions in the queue again and and it keeps giving the +1 missions with every additional fire station I build.