Update - "Redeeming Credit" confirmed. On December 18, 2011 a charge was placed for $22.16. I didn't notice this before but there was already a $0.10 credit balance from my prior payment that also had my demand stamped on it. The resulting balance due was $22.06 which was paid via PMO on or after January 5, 2012 for the same amount. On the coupon I stamped "DEPOSITED FOR CREDIT ON ACCOUNT OR REDEEMED IN LAWFUL MONEY PER TITLE 12 U.S.C. 411" in red letters.

On the new statement I recently received the Previous balance shows "$0.00" but shows Other Credits as "5.00." Under New Balance it shows "$5.00-"

Go figure. Definitely something interesting there.