This year, magazines reported 10.2 million subscribers to their digital editions, according to the Alliance for Audited Media — but apparently one magazine accounts for 3 million of those subscribers.Game Informer — a print and digital magazine that previews and reviews videogames — is the top circulating digital edition magazine for the iPad (we assume this excludes iPad apps). But the magazine isn’t actually sold independently — it’s part of a loyalty program by parent company GameStop, which bundles digital subscriptions to Game Informer with its PowerUp Rewards Pro Card. The loyalty card costs $14.99 for the year (there is a free loyalty card that does not include a subscription to the magazine).While bundling subscriptions with another purchase isn’t new (AARP is the top circulating magazine because readers get a subscription with membership, and Conde Nast and GAP have partnered to offer subscriptions to Lucky magazine), the fact that Game Informer’s subscriber base on the iPad is greater than Cosmopolitan and US Weekly combined does shed new light on the popularity and sell-ability of digital editions via the iPad.Most tellingly, Game Informer’s large subscriber base seems to indicate that direct subscription sales to digital content is not as easily achieved as the bare statistics seem to indicate.On the other hand, tying subscriptions to other membership perks is a definite selling (and retention) tactic that other publications could use to their advantage, especially since digital editions are sometimes more popular that app downloads. Overall, it may be the easiest way to transition print audiences to digital devices (and then un-bundle and upsell tablet app subscriptions, like The Economist does).Image: (c) meedanphotos via flickr.