More like 11 thousand if you start from Xin, plus the other 7 sets of 10,000 years thanks to Alaznist. Worth learning about the runelords just so you have context for why all their shit is still lying around.
Anyway, some fun, extremely minor facts: The Mindspin mountains are so named because, according to Orcish myth, Cayden Caylian led the greatest pub crawl ever there and it left everyone's minds spinning. The god of Murder hangs out directly underneath the Plane of Law. Princess Anastasia Romanov, rumoured to have disappeared in the Russian revolution, is the current queen of Irrisen, and Baba Yaga's granddaughter. One of Magnimar's most senior Pathfinders is an awakened gorilla. There's a 17th level wizard that lives in a tower on the Sun, and a 19th level wizard running an entire country of scientologists. There's a god of accidental deaths whose followers create OSHA violations in the hopes of causing deadly accidents.