Serious damage means any defect, other than color, which seriously affects the appearance, or the edible or shipping quality of the individual portion of kernel or of the lot as a whole. Any one of the following defects or any combination of defects the seriousness of which exceeds the maximum allowed for any one defect shall be considered as serious damage:

(a) Shriveling when more than one-fourth of the kernel is severely shriveled, or a greater area is affected by lesser degrees of shriveling producing an equally objectionable appearance;

(b) Mold when plainly visible on more than one-eighth of the surface of the kernel in the aggregate; and,

(c) Discoloration of the meat when more than one-fourth the volume of the portion of kernel is severely discolored, or a greater volume is affected by lesser degrees of discoloration producing an equally objectionable appearance.