It's normal for some cars to have their speedometer read a bit high, for safety and regulatory reasons. The car always knows how fast it's really going, within the bounds of mechanical possibility. It's only changed for driver display. My old B5.5 Passat and my Phaeton have the offset, but my 2018 Golf R doesn't... but in other markets the Mk7 Golf does seem to have a displayed speed offset. I don't know precisely what countries have what rules.
I have to deal with this sometimes for openpilot. I don't think there's any worldwide shipping configuration where the car displays two different numbers once it reaches steady-state cruise: both the displayed speed and displayed CC setpoint should present your true speed, or they should both be transformed/offset. Something is wrong here.
Given that you're seeing a constant positive offset at every speed, this does sound like problem with software/regulatory offset configuration. But how and why...
Code:
Address 17: Instruments (J285) Labels:| 4H0-920-xxx-17.clb-SRI1
Part No SW: 4G8 920 932 D HW: 4G8 920 932 D
Component: TDieRdw H79 0515
Revision: 28460
2 Serial number: 658110612596017
Coding: 13AF11000B41000C0D0000
Shop #: 19709 004 104857
Dataset: EV_RBD4K 004046
: EV_RBD4K_AU57.
VCID: 3038E665CAA244DB7FF-8064
No fault code found.
Do the "Revision" and "Serial number" fields appear like that in your original Auto-Scan, with the "2" between them? Or is that a copy/paste oops? If your instrument cluster puts out truncated/corrupted spam when asked for its Revision, that's bad, mkay? See this
example scan with a non-garbage Revision. It means the EEPROM is corrupted, possibly due to tampering. Do you know the full history on this car? Is it possible anyone has used non-dealer/locksmith tools to match new Immo keys, or to defeat Component Protection (not sure if either are actually applicable to this car) or used sketchy tools to tamper with the odometer?
If the Revision thing was just a copy/paste issue or a fluke, then take a look at the Coding value. Look for anything related to regions of sale (Europe/), markets, countries. Make sure it's set correctly. Failing something in 17-Instruments, look for the same sort of thing on 01-Engine, which controls the CC setpoint and relays it via CAN for the instrument cluster to display.
