Update:
Just got off the phone with what seemed to be a very competent Chase rep. I am being told that the business class upgrades come in the form of an EMAIL from Airtran. The email will contain voucher codes to be used for the upgrades. This is what I am being told. The Chase rep actually had to put me on hold and call Airtran.
What bothers me about this is that the promo -- while being a good promo -- isn't what it says. It says that the business class upgrades are on FIRST USE. Then they footnote that statement and say 6-8 weeks to receive the business class upgrades. So you get nothing at first use. The upgrades are given after 6 - 8 weeks of first use of card.
@zornoff - the 64 credits are a mistake. You may want to do nothing and leave them there, or you may want to convert them over to WN for "safe keeping." If they catch the mistake they will likely claw some of them back out.