The minimum balance due is the minimum amount that must be paid by the deadline for making payments. It is determined as 5% of the total of your unpaid balance, including all credit card fees.
In this case, if you bought Rs. 15,000 on the 15th of August and the due date for the payment is the 26th of September, the minimum amount due is Rs. 750 (about five percent of Rs. 15,000).