On a previous thread Sucro posted the following message to answer my question. I cannot respond on that thread for whatever reason so, I had to start a new thread. This is Sucro's message to me;
No no, you are wrong, you don't have to change GMAPSUPP.IMG to gmapsupp.unl, just copy-paste that file GMAPSUPP.IMG to your device-internal memory in garmin folder, or if you want maps on SD CARD, make folder Garmin, and copy-paste inside ...