What changed: Carrie used fewer credits this cycle (9 vs 10), had more cancellations/refunds (2 vs 1), and nothing expired yet. That's why she's carrying 5 into the final 6 days instead of the previous cycle's 3 expiring unused.
How this period reached 5:Started 12→−9 used→+2 returned→−0 expired→= 5 left
Current period activity · newest first · running balance
−1Credit #9 — Reformer + Some — All LevelsJun 21 · 5 left
−1Credit #8 — DynamicJun 20 · 6 left
+1#7 Dynamic returned — class cancelledJun 19 · 7 left