How do we count 19 cities?
Malbim: There are 15 Arei Mivtzar, three cities in verse 33, and Chukokah. Chelef and Alon are places, but not cities.
According to Rashi (12), also Aznos Tavor is not a city. It is close to the peak. Radak (34) holds that it is Kislos Tavor; perhaps it was in Zevulun. (PF)