It means that this train is being heavily overbooked, but the commercial managers are certain that this is temporary or multiple bookings being made by people. That is why the waiting list is allowed to be so high. You will it drop suddenly one day !
High Waiting Lists have run upto nearly 1000 yes 1000! They have to be manually allowed by the commercial managers. And it is because of analysis done on previous occasions depending upon the date, time and destinations. While most look at calenders to see weekends, I would also look at additional days which come together as festivals in the states being traversed by the train. For that you also need to consult a Panchang!! Plus...
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read the news daily to understand why there is a sudden rush on particular days for particular stations rpt stations, and from where the crowds will emanate (start)!! A multi-cultural digest is also useful. For instance on certain days, you will find a rush to Ajmer for the visit to the Ajmer Dargah.. so you can find a rush from Gujarat/Rajasthan/NDLS etc. Similarly, there is a rush on Krishna Jayanti for Mathura AND AGRA from surrounding stations like NDLS, Bharatpur, Agra, Tundla etc. This will also happen at Dwarka and Porbander.. so crowds from Mumbai, Ahmedabad, Baroda... There are many more examples..
In short the grouping of holidays with Sat/Sun is NOT the only indicator. You also have to know the Festival Days of all religions to see the possible traffic on that sections/routes, and the significant religious places.
Good wishes.