Allow me to help 
Yes with 4.4% you will nearly double after 16 ticks. The catch is that the population is calculated on a per planet basis.
Here's what I think Is going on:
Lets say right now you have a pop of 100k.
Population on any given planet will double every 16 ticks provided that planet has enough room for population to grow. Assuming no planets have reached max pop your overall pop will double. So in 16 ticks you have about 200k (199,162 to be exact).
When one or two planets reach max pop the population on that planet no longer grows. So that pop won't double. So starting with a current pop of 100k. If two planets with 10k pop each are maxed, then that means that only 80k pop are elegible for doubleing. This means that after 16 ticks your pop will go from 100k to 159,330.
I hope I explained that clearly.
Rehabilitated IC developer