According to the author of the book, this verse tells us about the land given to the Levites, who were special helpers in the temple. It's like saying they got special towns and places to live in and work from.
1 Chronicles 6:72: And out of the tribe of Issachar; Kedesh with her suburbs, Daberath with her suburbs,
This verse states that Jarmuth and its suburbs were given to the tribe of Zebulun, whereas 1 Chronicles 6:72 assigns it to the tribe of Issachar.
Joshua 21:29: Jarmuth with her suburbs, Engannim with her suburbs; four cities.