The query confuses..availability means the time lag till whch CK can be booked in morning, i.e. berth remain unbooked for proportionate time lag after booking opens!!
Or number of berth allotted for pair of stations in CK!!
If its time lag, then its tight & quite irritating to book..
If its about number of berth, thn u can check it just one night b4...
more... booking day, which will indicate beth count suffixed with #..