This field records the name of the previous FSM state that a single, one-time backup job that an admin (or a BackupPolicy) has queued against a UCS domain was in before its current one. Keeping the prior state alongside the current one lets an admin (or a support engineer reading a TAC case) reconstruct the exact sequence of steps a Backup's workflow passed through, which is often the fastest way to see where a failing backup/export actually went wrong. For a job that is now connecting to the remote server, this field would show the name of whatever step ran immediately before that, such as the local data-collection step.