What does 1 Chronicles 26:18 mean?

To Obed-Edom southward; and to his sons the storehouse.

To Shuppim and Hosah westward, by the gate of Shallecheth, at the causeway that goes up, watchman opposite watchman.

Eastward were six Levites, northward four a day, southward four a day, and for the storehouse two and two.

These were the divisions of the doorkeepers; of the sons of the Korahites, and of the sons of Merari.

Of the Levites, Ahijah was over the treasures of God’s house and over the treasures of the dedicated things.

The sons of Ladan, the sons of the Gershonites belonging to Ladan, the heads of the fathers’ households belonging to Ladan the Gershonite: Jehieli.