What does 1 Chronicles 26:15 mean?

Of these were the divisions of the doorkeepers, even of the chief men, having offices like their brothers, to minister in Yahweh’s house.

They cast lots, the small as well as the great, according to their fathers’ houses, for every gate.

The lot eastward fell to Shelemiah. Then for Zechariah his son, a wise counselor, they cast lots; and his lot came out northward.

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.

For Parbar westward, four at the causeway, and two at Parbar.