I would appreciate some help regarding the following 2 soldiers.

T. S. Knight (Thomas S. Knight) of Rapides Parish
6th Regiment Louisiana Cavalry
Company K

Allen F. Cryer of Rapides Parish
27th Regiment Louisiana Infantry
Company C
Substitute for Thos. S. Knight

Thomas S. Knight has one card in his CMSR, which is a surrender and parole record. At the bottom of the jacket there is a note that says refer to Allen Cryer of the 27th Infantry.

On the first card in the CMSR of Allen F. Cryer there is a note that says that he is a substitute for Thomas S. Knight of Rapides Parish.

Questions:
If Thomas Knight had a substitute, then why does he have a surrender and parole record with the 6th Cavalry?
In the spring of 1862 what was the age range of those who were required to serve?

Thanks,

Lottie