They publish a different number of satellites in every single place I have read. Some places they say 19000, some even more.
Guessing that in places where the cost of keeping the constellation filled out is considered, they quote smaller numbers, and for subscribers per satellite, higher numbers.
I pretty much go by the list on wikipedia, which reflects what the FCC has approved. That total is about 12k by 2027, and half that by 2024. I don't see the FCC approving more units until at least the 2024 benchmark, and they are currently only 40% of the way there.
Guessing that in places where the cost of keeping the constellation filled out is considered, they quote smaller numbers, and for subscribers per satellite, higher numbers.