(a) In order to allow for variations incident to proper grading and handling, not more than a total of 10 percent of the pears in any lot may fail to meet the requirements of grade: Provided, That not more than 5 percent shall be seriously damaged by insects, and not more than 1 percent shall be allowed for decay or internal breakdown.

(b) When applying the foregoing tolerances to the combination grade no part of any tolerance shall be used to reduce the percentage of U. S. No. 1 pears required in the combination, but individual containers may have not more than 10 percent less than the percentage of U.S. No. 1 required: Provided, That the entire lot averages within the percentage specified.