In set-up, the options for rolling the D6 should be:
1-3: Earthscape 10 or 12
4-6: Earthscape 9 or 16
(alternatively, if it's easier to remember, simply re-roll if you roll a 1-2 and use the 3-6 results as printed).
The top option (giving earthscape 13 or 14) should not be used, as those earthscapes are part of the map already and not meant to be repositioned.