it means that if you have another of the same item you can make a second-chance offer to any of the underbidders to enable a sale of another of the same item. I used to use second-chance offers when I got a high price for an item and I had another one. The offer price will be the maximum bid amount placed by the underbidder.
If you do have another of the same item, send a message to the highest underbidder and ask them if they would be interested in buying at their maximum bid. If you send a second-chance offer it will be valid for 24 hours.
If you do not have any more of the same item then all you need to do is ignore the message.
