That is one with a validity of 15 days and other with 30 days. So once you recharged this pack you will not be charged extra for using WhatsApp on your phone.So Enjoy Unlimited Social networking on WhatsApp just for Rs 1 per day. If you want to use WhatsApp for 15 days recharge for Rs 15 and for 30 days go for Rs 30 plan.
source: Tata Docomo | image credit: Tata Docomo