There are two versions. The sat nav has a database of what limits apply where and should display them on its screen. You can have this on the GTI no problem.
Then, in a Golf (not GTI as its not available) if you spec the lane assist or whatever the option is with a front camera then you can also spec the speed limit detection which uses that camera to detect the speed limit and display in the MFD overriding the sat nav when they differ on the assumption the nav database is out of date.
I am unsure of:
1) The exact option required (lane assist or whatever) which gives the camera but isn't allowed on the GTI, if I could be bothered to find the brochure its probably in there somewhere.
2) If it is possible to get the sat nav database to display in the MFD without this option (i.e. on a GTI). I suspect the answer is no. With VCDS? Maybe...