RB585375685CN is saying Unsuccessful Delivery

Tracking No. Status Location Destination Date
RB585375685CN Collection Guangzhou IN Mon, 30 Sep 2013 22:50:00 GMT
RB585375685CN Opening Guangzhou IN Thu, 03 Oct 2013 12:57:00 GMT
RB585375685CN Opening Guangzhou IN Thu, 03 Oct 2013 20:32:00 GMT
RB585375685CN Dispatching Guangzhou IN Fri, 04 Oct 2013 14:32:00 GMT
RB585375685CN Departure from outward
office of exchange Beijing IN Wed, 09 Oct 2013 12:37:00 GMT
RB585375685CN Delivery to airport Beijing IN Thu, 10 Oct 2013 01:10:00 GMT
RB585375685CN Arrival at inward office of
exchange Calcutta, IN IN Sat, 19 Oct 2013 18:20:00 GMT
RB585375685CN NULL IN IN Sat, 19 Oct 2013 19:40:00 GMT
RB585375685CN Dispatching Bangalore, IN IN Wed, 23 Oct 2013 15:34:00 GMT
RB585375685CN Unsuccessful delivery IN IN Fri, 25 Oct 2013 10:37:00 GMT

Above is the detail of tracking record. Please tell me why it is showing Unsuccessful delivery.