Size shall be specified in accordance with the facts in terms of one of the following classifications:

(a) Mammoth size. Mammoth size means walnuts of which not over 12 percent, by count, pass through a round opening 96/64 inches in diameter;

(b) Jumbo size. Jumbo size means walnuts of which not over 12 percent, by count, pass through a round opening 80/64 inches in diameter;

(c) Large size. Large size means walnuts of which not over 12 percent, by count, pass through a round opening 77/64 inches in diameter; except that for walnuts of the Eureka variety and type, such limiting dimension as to diameter shall be 76/64 inches;

(d) Medium size. Medium size means walnuts of which at least 88 percent, by count, pass through a round opening 77/64 inches in diameter, and of which not over 12 percent, by count, pass through a round opening 73/64 inches in diameter;

(e) Standard size. Standard size means walnuts of which not over 12 percent, by count, pass through a round opening 73/64 inches in diameter;

(f) Baby size. Baby size means walnuts of which at least 88 percent, by count, pass through a round opening 74/64 inches in diameter, and of which not over 10 percent, by count, pass through a round opening 60/64 inch in diameter; and,

(g) Minimum diameter, or minimum and maximum diameter. In lieu of one of the foregoing classifications, size of walnuts may be specified in terms of minimum diameter, or minimum and maximum diameter: Provided, That not more than 12 percent, by count, pass through a round hole of the specified minimum diameter, and at least 88 percent, by count, pass through a round hole of any specified maximum diameter.