Explosives

In the Overlord book the Airborne Engineers and Engineer Squad (Normandy) can be equipped with explosives. In the unit descriptions the rule says that to use the explosives the unit must start adjaacent to the target and on an advance order get all members at least 4″ away from the target. At that point the explosives can be detonated.

If the target is a building or fortification that the unit can occupy, can the unit start the turn inside the target, advance out and detonate? Adjacent or inside they have access to the target and on an advance order can get everyone outside of 4″. It seems logical that they could be inside, set the explosives and exit, but the brief rule statement says adjacent as opposed to “touching”.