I don't think that information is correct.
I had the option of updating the system to 8gb when customizing it, but I realized it would be cheaper to do it myself when it arrives.
It looks like it will take up to 8gb Kingston PC 8500 DDR3
This is the part number from the Toshiba site - KTT1066D3/4G
If found a few places that sell it, I may pick it up from New Egg