33. If the contributor, at the time of his death, has not paid the full amount payable under sections 27 to 29, the balance may be recovered out of any allowance payable, under this plan, to his surviving spouse and children, in either of the following manners as chosen by the beneficiary:(1) either by the deduction of a lump sum from the allowance, as soon as it becomes payable;
(2) or by equal deductions from the allowance over a period equal to the fraction of the period referred to in section 31 and for which no contributions were made pursuant to sections 27 to 29; such deductions shall not exceed 30% of the gross monthly payments.