This can be stated in active form. Alternate translation: "Four Levites guarded the pillar to the west" (See: [[rc://en/ta/man/translate/figs-activepassive]])
The numbers "four" and "two" refer to guards. Alternate translation: "four Levites stationed at the road and two Levites stationed at the pillar" (See: [[rc://en/ta/man/translate/figs-ellipsis]])