The attached figure shows that scratch depth is proportional to scratch width. Measuring the scratch width using a microscope we can roughly estimate the scratch depth.
When the scratch depth is approaching the apex width we have to expect that the strength of the edge will be decreased.
Example: For an edge with 250 gf BESS "C" reading we can assume that the edge apex width is some 0.5 μm. The red line in the attached graph tells us, that a scratch near the edge, which has a width more the 5 μm will decrease the strength of the edge, because the scratch depth is equal to edge apex width 0.5 μm.
When the scratch depth is approaching the apex width we have to expect that the strength of the edge will be decreased.
Example: For an edge with 250 gf BESS "C" reading we can assume that the edge apex width is some 0.5 μm. The red line in the attached graph tells us, that a scratch near the edge, which has a width more the 5 μm will decrease the strength of the edge, because the scratch depth is equal to edge apex width 0.5 μm.