What I\'m doing is executing an AppleScript inside of Cocoa. It returns some data as a NSAppleEventDescriptor, which NSLog() prints like so:
That's a record, not a list. Try descriptorForKeyword:, passing the constant matching the four-character code you want. (The constants are declared in the Apple Events headers.)
descriptorForKeyword:
[[aDescriptor descriptorForKeyword:keyAEKeyData] stringValue]