There are two types of AI-credits, the once you have while your subscription is active are topped off each time the subscription renews, i.e. if you are on a monthly premium subscription and have 863 credits left on the date of the renewal that will be reset to 1000. If you cancel your subscription the subscription credits will reset to 0. The second type of credits are the Credit Packs, these credits will never expires and are counted separately from the subscription credits. If you have a subscription and bought a credit pack your subscription credits will be used first and when they are gone we will start using credits from the Credit Packs.