If, when the opening is being made, it appears that the number of square yards of surface to be cut is greater than is shown by the application, the applicant shall immediately pay the remainder of the fee due the town. If, when the opening is completed, the number of square yards of surface actually cut varies from the number for which the fee was paid, the proper adjustment shall immediately be made by the applicant or by the town.
(1940 Code, Ch. R, Art. I, § 4)