Two layers, and one of them makes the contact
The underside is cotton with the silver thread woven into it; that is the side you put against your skin. The top side is soft polyester and takes no part in the grounding. The less fabric in between, the better it works: bare arms or legs on the blanket do more than a blanket over your clothes.
The label says 2 percent silver thread, less than the 5 percent in the sheets. That is because it is calculated across the whole blanket, polyester included. Work it back to the cotton side and you get a good 6 percent, so slightly more than in a sheet.