“This is the list of the people of Israel, the heads of families, the commanders of the thousands and the hundreds. These officers served the king in all matters concerning the divisions that came and went, month after month throughout the year. Each division numbered twenty-four thousand.”
King David had a strange set up. Each month there would be a new commander. I guess that it made it easy for everyone. Each monthly division had about 24,000 troops. Thus there were 12 groups, one for each month. That would mean that King David had 288,000 men, which seems like an unrealistic number. Apparently this was an attempt to emphasize the 12 tribes, but in fact there was no attempt to include the 12 tribes.