What does Joshua 17:9 mean?

The border went down to the Kanah Valley, south of the valley. Some towns in the valley belonged to Ephraim, even though they were inside Manasseh's land. The border ended at the sea. Joshua 17:9 - Modern Text Bible

(Again, the boundaries were mixed, with Ephraim having towns inside Manasseh's area, and the border stretching all the way to the Mediterranean.)