The sefar (=census). This is a noun, in the pattern of eyal (=strength; Ps 88:5), serad (=service; Exod 39:1), and she’ar (=remnant; Isa 10:21).

By which [Solomon’s] father David had counted [the alien-converts]—as it says above: “David gave orders to assemble the alien-converts living in the land of Israel, and assigned them to be hewers” (1 Chronicles 22:2). But later on Solomon counted them again, because their numbers had grown since the time he became king. It is possible that these alien-converts were the remnant of the Amorite, Hittite, Perizzite, and Jebusite nations, consistent with what the text says just below (8:7); for Solomon subjected them to forced labor “to this very day” (ibid. 8:8) to perform his tasks and [to work on] the cities he arranged to have built. They are called alien-converts (gerim) because they were not idol-worshipers; for in the days of David and Solomon, when the Israelites had the upper hand, they did not permit them to worship idols. It was on this condition that they permitted them to reside in the land; and David and Solomon made them into hewers, porters, and general laborers (v. 17).