Could that number de derived from this statement???

"THE eleven States of the Southern Confederacy had, in 1860, a military population of 1,064,193 with which to confront the 4,559,872 of the same class, belonging to the other States and Territories. This number was largely supplemented during each successive year of the war by those who attained their eighteenth year of age, at which time they became liable to military duty."

http://civilwarhome.com/confederatelosses.html