By late 1861 Confederate authorities realized that the war could last for quite some time. They also understood that twelve-month enlistments would soon expire, and the armies disband as a result. To remedy the situation Congress passed a military "stimulus bill" called the furlough and bounty act. Each man who reenlisted for the war would receive a furlough and a fifty-dollar bounty. We would call it a signing bonus. You could do this anytime before the end of your twelve-month enlistment.
Men who took advantage of this offer could join a different command. A number of Mississippi soldiers stationed at Pensacola did exactly that, joining Felix Robertson's artillery company in December of 1861. Apparently this man elected to reenlist in his own regiment -- I've not reviewed his service file.