People can count to 344. If you divide up the work among 43 people they only need to census 8 fortresses apiece.
Keltham doesn't pursue this further, though; it matches too much other strangely missing competence to seem relatively anomalous. He just needs to keep track better of whether the incompetence tends to get in the way of anything that might possibly maybe want him to be anywhere but Cheliax.
"Sorry for even more basic questions but remind me of how many hours, or days, of unskilled labor, it takes to buy a teleport to the Worldwound from Tian." Does the basic picture on international trade even make sense here.