Symptoms
This issue occurs when you send or receive a file which is larger than two Gigabytes (GB) in an instant message (IM) conversation in Microsoft Lync 2013 (Microsoft Skype for Business). When this issue occurs, the size is always displayed as 17179869183.5 GB in the file transfer tile.
Resolution
To fix this issue, install the February 9, 2016 update (KB3114732) for Lync 2013 (Skype for Business).
Note Lync 2013 was upgraded to Skype for Business in April 2015.