Generally In Indian Railways Charting of the Train Is Done 4 Hours Before The Scheduled Departure of the Train From Station But Only if its Departure Time is After 12 Pm If it Is Before 12 Pm Than Charting is Done One Day Before At Around 8 Pm . now after this Charting 2nd and final charting is done 30 mins before the departure of the train , After the first charting all remaining tickets will be sold at 10 % Discount as the current availability Ticket . you can book current availability tickets after the first charting get done till 30 mins before of the train’s scheduled departure , but what i will suggest you that after the first charting quickly book tickets don ‘t wait for a while because in any time this booking of the tickets can get closed . now lots of time it is possible that you will see waiting in general quota & tatkal Quota but in this current availability you will easily get confirmed seats with 10% discount so ,thats set for the current availability Tickets in Indian Railways With 10% Discount . NOTE : in trains like Shatabdi , Rajdhani , Duronto , Humsafar and Suvidha 10% Discount is applicable on a Increased Dynamic fare .