Build orders: which villagers to use for building?

So Ciceros build order guides and in turn the build order scenarios specify exactly how many villagers should work on which resources.

They also specify which buildings should be built. Which villagers should I use for this? There are no extra vills in the BO, and if I pull them off of a resources, the numbers for the resource are obviously incorrect.

For example, the Archer Rush build order requires you to build a Barracks, 2 Archery ranges, 1 Blacksmith, not to mention all the houses and potentially walling. That is a significant amount of villager work time that to me looks unacccounted for! That means that I'm missing 2-3 villagers on a resource for a long time.

Should I use food villagers? Should I use Wood villagers? Should I just make "extra" villagers that are not described in the BO?