Are you mentioning the ElementWallDistance?
Let’s say I want to exclude 5 inches from the wall of the old mesh, the main drawback here is that ElementWallDistance includes all cells whose centroid is located less than 5 inches from the wall, which means the outer boundary of this region will not generally be a smooth surface, although it could be depending on how the mesh is generated. Also depending on how many different quantities are required, it could be tedious defining a large number of expressions.
However, the Normal Distance let me keep whatever 5 inches away from the boundary which is what I am looking for.
The reason I am doing this because, for meshing having high number of elements, most of elements are close to the wall (the geometry is a big room). Hence, if I am calculating average value for the velocity, the close-to-boundary element values will dominant the calculation which is not very accurate for my analysis.