Lieutenants, Sergeants and Corporals were numbered according to their rank. Each one had a specific roll according to the military instruction of the day.
For instance, the senior non-commissioned officer was 1st Sergeant. Among other duties, he kept the company book and called roll.
If you're interested, we can check on a pension application in this man's name. One may have been filed in either Alabama or Georgia. The message board can also offer copies of the Reeves service file.