From: Dallas, Texas
From the manual:
The combat value of each defending unit is modified by multiplying the CV by one plus the total fortification defense modifier, which is the sum of the terrain modifier and the fort level. For example, a defending unit in a Light Urban hex (terrain modifier of six) with a fortification level of three would have its CV multiplied by ten (1+6+3) during combat.
22.214.171.124. Terrain CV Modifier
AFV and combat vehicle type ground elements will have their CV (26.1.4) reduced by half when attacking or defending in urban, heavy woods, swamp, broken and mountain hexes. Infantry type ground elements will have their CV doubled when in urban, heavy woods, swamp, broken and mountain hexes.
Using their example, what if you have an armored unit defending in a light urban hex with a fort level of 3 (and for simplification, assume all of its elements are AFV and combat vehicle type). Would the unit have its CV multiplied by 10 (per 15.3.1), then divided in 2 (per 126.96.36.199), for a net effect of 5x? Or do the AFV and vehicle elements get no bonus from the light urban hex, and its multiplied by (1+3)=4 (just for the fort) then divided by 2, for a net effect of 2x?