Need some help with population.

I’m trying to make a smaller island, in the 20k square mile range, but no matter what I set for the units, it doesn’t change the amount of population per cell, and even with minimum habitability of 1%, by generating 3k cells of land, the FMG gives a population of around 2 million. Does anyone know of a way to decrease the per-cell population other than habitability, or perhaps a way to decrease the number of cells. I might just have a generate an archipelago and then adjust the height map to erase all but one island, but that seems a round about method.