If the train is diverted via Perambur - it will be earlier arrival at NZM - Like if it leaves CBE at 16:15 PM and can arrive MAS at 23:35 PM and to leave MAS at 23:50 PM and can follow TN and reach NZM at 09:00 AM.
This would save 5 hours of travel time. Return could leave NDLS at 23:45 PM and can reach MAS at 09:00 AM to reach CBE at 16:30 PM