4(1)If, although the registered rent is higher than the rent payable under the tenancy, the lump sum equivalent of the difference is less than the premium, paragraph 3 above shall have effect as if P were the lump sum equivalent.
(2)For the purposes of this Schedule, the lump sum equivalent of the difference between the two rents referred to in sub-paragraph (1) above shall be taken to be that difference multiplied by the number of complete rental periods falling within the period beginning with the grant, continuance or renewal in respect of which the premium was paid and ending on the relevant date.