Here's the short version
Carrie renewed her 12-credit pack on June 1. Since then she's booked 9 classes — but 2 of those were cancelled and the credits came right back. So she's really used 7, which leaves her with 5 credits available good through July 1.
The quick math: 12 purchased − 9 used + 2 returned − 0 expired = 5 left. Nothing has expired.
Only 6 days left in this cycle — a good moment to nudge Carrie to book a class or two before it renews.