Now how does population grow?
The population on a planet doesn’t start at maximum capacity, when you first gain a planet you will get a starting population of 1x its size, for example, a 250 sized planet will start with 250 population. Every tick the population will grow with a base growth of 4%. This means your 250 population will grow to 260 people. And a tick later 270 people and again a tick later 281 people and so on. This pop growth is decided in your race in the form of a pop growth bonus. 0% bonus means a growth of 4% per tick. 50% bonus means a growth of 6% per tick. -30% bonus means a growth of 2,8% per tick. This is basically how population works.