HI Jodie12
Thanks for your post.
Aging customers are determined by two factors, the payment terms on the card and the Statement Date in the Print/Email statements window. Based on your credit terms of payment due 30 days after the end of the month. If you selected the statement date 30/5 the due date will move into 30 days as it was due in July. current is May and June. I hope this clarifies the issue. You can check on our Help Article: Credit Terms, this contains more information that can help you and serves as your reference.
Let me know if you need further assistance with this. I am happy to assist you.
Thanks,
Cel