I believe you are correct. MIB1 Discover Media Navigation had a 5.8" screen. Then went bigger with MIB2. The info I gave above was taken from V.W. U.K.'s site so is for the current versions. I understand the specs for MIB1 Discover Media Navigation and Discover Navigation Pro are as follows -
Discover Media Navigation
5.8" Touch Screen with 400x 240 Pixel Resolution
2D/2.5D map navigation (Europe) with voice control
CD drive MP3/WMA
Music playback from MP3, WMA, AAC files with title display from SD and AUX IN
USB, AUX-IN, SD (2x) (Aux and USB require optional connection cable) - only 1 SD card available for music, other SD card contains Map data
DAB, FM and AM radio reception
4x20 watt output (front and rear speakers)
Bluetooth connection for phone and media (HFP, A2DP *, AVRCP **)
Discover Navigation Pro
8.0" touchscreen colour display with 800 x 480 Resolution
Faster 3d Display Engine (graphics Chip)
3D map navigation (Europe) with advanced voice control
DVD Audio/Video
Film playback from AVI, MPEG, Divx, H.246, and DVD from SD, USB and DVD data carriers
Music playback from MP3, WMA, AAC files with title display from SD and AUX IN
Gracenote database, podcast playback and jukebox
Internal 64GB memory as SSD - (Solid State Hard Drive) - 30GB can be used for music, etc.
USB, AUX-IN, SD (2x) - both SD cards available at all times (maps are stored on the HDD)
DAB, FM and AM radio reception
4x20 watt output (front and rear speakers)
Bluetooth connection for phone and media (HFP, A2DP *, AVRCP **)
Some good info here for anyone who is interested. This is for systems launched with the first of the MK7 Golfs -
http://telematicsnews.info/2012/10/25/exclusive-volkswagens-new-infotainment-line-up_o3251/