For every train, there can be one or more charting locations. For example, consider train no 12842 MAS - HWH Coromandal exp
Its first charting Location is MAS. Next, VSKP comes under RL quota. Hence it becomes second charting location. So, for boardings between MAS and VSKP (excluding VSKP), Charting will be done at MAS, generally 3-4 hours before the train's dep from MAS.
The same thing applies from VSKP onwards until next charting location.