File size differences

My Book shows up as Drive F on my PC. From Windows Explorer it shows 734 GB of used space. However, from WD SmartWire it it shows 1047.8 GB used. In my music folder in Windows Explorer is shows only 208 GB but SmartWire shows it as 524.9. No wonder I lost the ability to backup changes. SmartWire thought I was full but it was not physically possible. any thoughts?

Perhaps it would be best to contact WD Support about this. You can do so over the phone or via E-mail.