To my account agent's credit, he got back to me before 1 PM today.
Apparently, the credit I got for the mysterious $480 was an error. It was a refund for game one of the NLCS on my regular strip, which makes sense (4 x $120 per seat) and had nothing to do with my extra single games seats (4 for NLCS Game 1 and 4 for NLCS game 2). All money for the regular strips should have been rolled into the balance for my 2013 season tickets. A full credit for the extra single games was issued Friday, with only the $4 processing fee for the whole order held back. I guess it will show in my credit card at some point.