Help Understanding Franking On This 1870-S Cover

A cover sent to Gen R. K. Scott.

It appears to have been first sent from Cincinnati Ohio on Aug 24. Destination, Columbia S.C. But..., only the one cent stamp was canceled in Cincinnati.??
Then on Aug 30, it was forwarded from Columbia to Napoleon, Ohio. The three cent stamp being canceled at Columbia.
There is a REC'D Toledo O backstamp.

If you check out Gen Scott's career, Columbia and Napoleon both make sense. He was Governor of South Carolina and retired to Napoleon in 1877. So it's not surprising to see a letter following him.
Even the "Army of Tennessee" notation makes sense. That's where he served during the war.

I don't understand why one cent going from Ohio to SC. And then three cents to send it back to Ohio?

Also note the logo in top left corner, on the eagle's chest reads, "Dirty Hounds US".

EDIT: it reads "Forty Rounds US". It appears to be the 13th Regiment.?

The one cent rate cover the shipment from Cincinnati, Ohio to Columbia, SC probably as an unsealed circular. The 3 cent stamp paid the forwarding postage from Columbia to Napoleon, OH (probably sealed).

Ahhh unsealed rate.

I wonder who paid the three cents?

BTW...it reads "Forty Rounds", not Dirty Hounds. It's the 13th Regiment.

An interesting man! And, I think, the last Republican governor of South Carolina before former slave-owners undid Reconstruction.