This is the internal integer ID of the QoS policy Definition that this deletion task is in the process of removing. Deleting a QoS definition isn't instantaneous — UCS Manager has to unwind every reference to it on every fabric interconnect and adapter that used it, and this task object is what tracks that cleanup to completion. This lets UCS Manager (and an admin reading a support bundle) tie a specific deletion task back to the exact policy object it targeted, even after that policy object itself has been removed and its Dn is no longer resolvable.