In order to allow for variations incident to proper grading and handling in each of the foregoing grades, the following tolerances, by weight, are provided as specified:

(a) U.S. No. 1 Halves, U.S. No. 1 Halves and Pieces, and U.S. No. 1 Pieces grades:

(1) 0.05 percent for shell, center wall, and foreign material;

(2) 3 percent for portions of kernels which are “dark amber” or darker color, or darker than any specified lighter color classification but which are not otherwise defective; and,

(3) 3 percent for portions of kernels which fail to meet the remaining requirements of the grade, including therein not more than 0.50 percent for defects causing serious damage: Provided, That any unused portion of this tolerance may be applied to increase the tolerance for kernels which are “dark amber” or darker color, or darker than any specified lighter color classification.

(b) U.S. Commercial Halves, U.S. Commercial Halves and Pieces, and U.S. Commercial Pieces grades:

(1) 0.15 percent for shell, center wall, and foreign material;

(2) 25 percent for portions of kernels which are “dark amber” or darker color, or darker than any specified lighter color classification, but which are not otherwise defective; and,

(3) 8 percent for portions of kernels which fail to meet the remaining requirements of the grade, including therein not more than 1 percent for defects causing serious damage.