Colour depth from PRO3X dvi port

I have a 6410 on the above docking station. Via the dvi port video signal is sent to the HDMI input of a high def TV. The TV shows the signal is 1080p but the colour depth is 12 bit. The Nvidia display settings indicate the output from the graphics card is 32bit.

After looking at all sorts of settings am now wondering if the the different colour depth is the cable converting from one socket type to another.

Is it the output from the PRO3X 12 bit?