: This part looks like a timestamp in Unix format, representing the number of milliseconds elapsed since January 1, 1970, 00:00:00 UTC. Converting this to a human-readable date and time:
If you must inspect it (e.g., legacy air-gapped system):
Symantec Endpoint Protection 14.3 Installation and Administration Guide during this upgrade process? Symantec Endpoint Protection - Broadcom TechDocs