You can add up to 3 Gift card codes per account, of either Rs 20 or Rs 25 or a combination of both. You will not be able to add 3 codes of each denomination. So you can get a maximum benefit of Rs.75 in one account.
You can add the codes up to the 30th of December post which the program will stop.
Along with the KitKat, you will get a scratch card containing a 17 character code. You need to visit http://www.amazon.in/addgiftvoucher and enter the code beneath the scratch. You need to enter the code that you see once your erase the scratch under the heading ‘Voucher code’.
See this offer on Amazon | FAQs | Terms & Conditions