Use the attribute attached to the Component:
buildnumber.sequence
Even if you may not want to use persisted build attributes for major, minor and patch it still may be a good idea to use it for the sequence. This enables that sequence numbers are sequential across projects (maintenance projects and development projects) and any rejected builds will not cause fall-outs between the build sequence attributes. Don't use this option if the account running the job doesn't have access to write new values to ClearCase.
See more details regarding this option on the PCUM wiki.