Not a typo at all. Kintargo is intended to be a small city; one of the reasons it's small is that it takes a certain amount of bravery to live in what is essentially a chaotic good city within the borders of a lawful evil nation.
Feel free to adjust the numbers if you wish, but keep in mind that if you make the city too large it becomes too powerful and important and thus less logical that Thrune ignores what's going on there, even BEFORE the events of Hell's Rebels start.
By keeping it as Cheliax's smallest city, it remains status as a "backwater" and thus a more logical place for a rebellion like what's detailed in Hell's Rebels to take place.
Which means 12000 Kintargans (and the rest of Ravounel) taking on the might of Cheliax. Guess I would have a harder time explaining that to my players than boosting the city to 30k inhabitants.But thanks for the confirmation