imputation, the first panel of this sequence (30lbs/14kgs) is a duplicate of the eighth panel (150lbs/68kgs) and the upper half of the second panel is a duplicate of the upper half of the third panel. The overall balance of dark and light pixels can be seen with the Photoshop histogram option that displays lines whose height represents the count of pixels corresponding to total black (a level of 0, on the left) to total white (a level of 255, on the right), as shown below.
Of the 7504 pixels commonly selected from each panel, this panel had a count of 4781 light pixels (those with levels 133...255). Repeating this for all the panels (1 through 14), the total number of light pixels is 33651, so that panel 6 accounts for 4781/33651 or 14% of the light colored wear. The other panels can be similarly computed finally resulting in the rounded wear percentages shown in the bar chart below.