Originally Posted by bgriff

Some of the seats show up that way at check-in as they are blocked until T-24. They are labeled as C+ onboard and you still receive the free drinks and other perks of C+.

Doesn't really matter for medallions since by T-24 all medallions can choose C+ for free, but a non-medallion might be able to get into those seats for a bit cheaper than other C+ seats, not sure what the price difference is.