Purchasing credits effectively unlocks your email address, allowing you to generate unlimited codes up to 100 at a time. Batches of more than 100 codes will deduct credits from your balance.
For example: if you purchase 1,000 credits your balance becomes 1,000. If you generate just 100 codes, your balance remains at 1,000. If you then generate 500 codes, 400 credits are deducted from your balance, making it 600. You may continue to generate up to 100 codes at a time indefinitely once all credits are consumed.