This document explains why ticket reference numbers may not be consecutive when created in CA Service Desk Manager.
In order to minimize SQL requests against the key_control table, the system will reserve six ticket numbers in memory and increment the next ticket number by six in the key_control table. If all six are used in the session, the system will then allocate six more and increment the next ticket number in the table by a further six.
Service Desk Manager ticket reference numbers may be skipped if Service Desk is recycled or if a ticket creation is cancelled. If you start the system and open a new Call Request, Cancel it, then shut down the Service Desk Manager service - the next ticket opened will be +six more than the previous one.
CA Service Desk Manager was designed this way to minimize locking and I/O on the key_control table in the database. This improves overall performance.