Not sure I understand your availability stats. What flight is it?

Usually J/C would be the same thing on CE (fully flex), with I being discount and R being sale. So you're saying that there are 5 seats available for sale, but 8 unallocated seats. How does this constitute overselling? Thats underselling if anything.

Secondly, seating policy is described in the seat-allocation sticky, but yes, they're in limbo until checkin. No unusual I suppose for CE to have many flex/status pax. Depends on time/destination.