500 credits ($50 value) or Adventure Park arcade games or attractions with scanners.  No expiration.  No cash value.

From the Adventure Park website:

Adventure Park USA is Maryland's largest family entertainment center. With everything from our Miniature Golf Courses to our Rock Wall and Hang 'Em High Ropes Course, we have enough adventure for the whole family. We even have summer camps for kids! Stay up-to-date with our Event Calendar and start planning your fun-filled trip today. Let the adventure begin!