what does it mean by amount of walls for achievements like Great Walls, Field Construction and Military Construction

I’m suck on task two of the Delhi Sultanate Mastery. “Construct 10 Palisade Walls during the Dark Age (I) without using Villagers.”

I have created 10 continuous walls between clumps of trees and mountains using just spearmen in the dark ages no go the number over the wall icon when I click on the spearmen is 30 what does that mean walls or wall segments?

i have created just 10 using just spearman also in the dark age no go. do I have to delete the villagers gathering resources before i start constructing the walls?

any help would be appreciated