The entire sentient population of Genertela is approximately 52 million (46 million humans, 6 million non-humans), which is comparable to the population of the Roman (45-60 million) or Han Empires (59 million) at their height. The Lunar Empire in comparison, includes about 9 million beings. The Kingdom of Seshnela is less than a third of that.
Genertela itself is about 3.5 million square miles, or about 20% bigger than the continental United States.
As an aside Genertela is significantly bigger than the Ancient World of the Middle East plus Greece and Italy.
At 10.8 million people, Fonrit has a greater population than the Lunar Empire. Although less than 3.5 million belong (literally) to the largest political entity. And collectively the East Isles are more than half the population of the Lunar Empire.
