Ahh yes, the scale of the map. Well, the Elemental Plane of Fire is always changing and never stays the same unless a being with great power wills it to be so. With that in mind, it becomes a little harder to scale a map with exact measurements. It can be imagined that the map viewer just needed some kind of unit of measure when they enter the plane so that they can hold on to what little reality is left in this everchanging plane. Is it four leagues or one mile increments in this map? Thats up to the players of the game to find out. That's why no unit of measure is given.