We have a Polo 2012 which appears to have an issue with the MFD in that it does not display the digital speedo just shows ---, also no speed sign recognition.
Neither. You use it to manually set a maximum speed that when exceeded, will display a warning on the display. The digital speedo is a separate display that may not be present on your vehicle but could possibly be added by coding.
@jouster can probably help you more with the specifics of that. You need an interface to the OBD port & some software to carry out the change. That's even if it's available on your model.