(1)An advance shall be recovered from the subscriber in such number of equal monthly instalments as the Chairman may direct; but such number shall be less than twelve unless the subscriber so elects or in any case more than twenty-four. A subscriber may at his option, make repayment in a small number of instalments than that specified. Each instalment shall be a number of whole rupees, the amount of advance being raised or reduced, if necessary to admit of a fixation of such instalments.