In the railway board uploads..its clearly mentioned as...
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At the time of preparation of charts of Rajdhani / Shatabdi / Jan Shatabdi Exp trains…after adjusting RAC/Waitlisted passengers and upgrading the passengers of lower class…if any..if the accommodation is still vacant. The system will automatically update the Duty Pass waiting list and remaining vacant accommodation, if any will be offered for booking at the current booking counter as is presently being done.