Gin Rummy Premium is a subscription and will automatically renew. It renews automatically every month or every year, depending on the terms of your subscription. Your iTunes Account or Google Play Account will auto-renew unless auto-renew is turned off at least 24 hours before the end of the current subscription period.
You can change your term or stop automatic renewal using the Settings app. Follow the steps under “How do I stop or change my subscription?” elsewhere in this FAQ.