Gigabyte = 1,000,000,000 bytes
Gibibyte = 1,073,741,824 bytes
160,000,000,000/1,073,741,824 = 149.0116119384765625GiB
I have heard that there is a lawsuit in process similar to that with Monitors in the past when they used list the size different to the actual viewable size.
I guess that's why they all list the size, and below it, the viewable size; just like coffee cups always says "warning, as you'd expect when you order hot coffee, contents are hot."
Due to the way CRTs work, the electron beams simply can not scan to the edges of the front glass pane and produce visible light.