Building time


I have never noticed this before....

Quite often when I que a building like barracks lvl 7 I get like 9 min building time but however when I que barracks lvl 8 in the same city it gets like a 3 min building time. It seems to happend randomly in random city.

I havent played for a while so dont know if its just a glitch or really a bugg or even content I havent played with before.