I am running Mac OS X El Capitan 10.11.6. My 2TB Samsung T3 only shows 250GB Capacity. I have installed the activation software from: http://www.samsung.com/semiconductor/minisite/ssd/download/portable.html
I have formatted the drive using all available options under Disk Utility.
For an $800.00 hard drive that only has 1/8th of it's advertised capacity, this has turned out to be an enormous waste of money.
diskutil list
would also be useful