Four CHUNKS (10x10) - w010n40 e000n40 w010n50 e000n50 make up the European space, chunks e140s30 e150s30 e140s40 e150s40 the eastern Australian space, and the default KSFO (San Francisco) space is just two TILES (1x1), w123n37 and w122n37. The missing 'maps', tiles, are where there is no land, so SG/FG chooses to NOT have scenery tiles for 'all' water areas. Viewed in Atlas, these maps will be overlaid with Airport, and NavAid information.
This MAP MAKING should be done BEFORE you load Atlas, and it is better to cover more than the specific area of the flight... It is sort of synonymous to heading out to purchase the arial maps, before flying in the region.
In my case this was as simple as running
@call runmap temp "--fg-scenery=\\Dell02\scenery-1.0.1" "--chunk=e140s30" "--chunk=e150s30" "--chunk=e140s40" "--chunk=e150s40"
and for Europe
@call runmap temp "--fg-scenery=\\Dell02\scenery-1.0.1" "--chunk=w010n40" "--chunk=e000n40" "--chunk=w010n50" "--chunk=e000n50"
and wait the time ;=)) Note Map had no problems with my UNC path to a linux (Ubuntu) machine...