Is that number accurate? If so, I think it's wild (no pun intended) that humankind knows the exact number of animals of that species, globally.
We are talking about a few families of gorillas, some of which are tracked daily. There is a massive conservation effort on these animals, at least in Rwanda and Uganda, they all have names and I don’t think a gorilla is born without someone knowing about it
So we're tracking (population / avg_group_size + misc_males) objects, as opposed to the entire population.
Example on the other end would be snow leopards (130+ sq km) and grizzlies (380+ sq km), which are mostly solitary and have huge ranges.
At the worst point their numbers dropped to the mid 100s.
The main threat to them is poaching, and local wars.
For further info: https://gorillafund.org/