Meaning of Indian Railway quota code: CK
Tatkal quota. This denotes the seats earmarked for sale under Tatkal scheme (i.e. sold one day before the train departs, with some extra charges). Due to high demand in most trains, it is not easy to book a ticket under this quota unless you are among the first few people at the counter when booking starts. Currently the booking starts at 10am the previous day of journey. This is also available for online booking on IRCTC at the same time.