The stated cause being “This problem occurs because the NTFS driver exhausts its resources when it tries to extend the volume.” The KB also details how to fix.  But I’ll include the four step fix that worked for me here too:

  1. Open an administrative Command Prompt (Right click “Command Prompt” and select “Run as Administrator”) and Run Diskpart
  2. At the DISKPART> prompt, enter list volume
  3. select volume # (where # is the number of the incorrect volume)
  4. extend filesystem

Now the file system size should match the extended partition size.

KB832316 – The partition size is extended, but the file system remains the original size 
when you extend an NTFS volume