Population Growth Question

Hi All, So I noticed something which I thought was strange.  On my homeworld I build a Krynnaic Alter and a Torian academy granting me four citizens.  I noticed an odd thing happened when I built the Torian Academy, the turns till next citizen jumped from 28 turns to 40 turns after the torians arrived. 

 I suspect there was a jump to 28 weeks when I built the Krynnaic alter. What happened?  Is this a bug or is because I only have one human on the planet? Currently all my other core worlds have better growth than my homeworld which were populated with humans.  But aside from the random jump how many population points does it take to produce a citizen?  5.55/wk is decent no?

Thanks for the advice/feedback.  See the screenshot below: