What was the census?

"A chapter of difficulties. First with reference to the numbering of Israel. The sin lay in the spirit of reliance upon the army, the horses, chariots, and men, rather than upon the Lord. With reference to the numbers given. Here Israel has 800,000, Judah 500,000, total 1,300,000. In 1 Chronicles 21., Israel has 1,100,000, Judah 470,000, total 1,570,000. Rather a startling discrepancy; there must be something omitted in this chapter. Yes, there was a standing army of twelve chief fathers, each had 24,000 men, with their officers 25,000 probably, that is 300,000 in all (see 1 Chronicles 27.) the total will then be 1,600,000. If we add to the account in 1 Chronicles 21:30,000 men, which are believed to have been kept on the Philistine border, we shall then in both cases have the same total, 1,600,000 men In any case these numbers show a population of eight to ten millions in the Holy Land at that time.
1902 Christadelphian p 568