In its application to the valuation of a policy of which the sum assured or guaranteed has been increased as mentioned in paragraph 11 and the increase has been amended under regulation 6 or 8 of the Industrial Assurance (Life Assurance Premium Relief) (Change of Rate) Regulations (Northern Ireland) 1989, this Schedule shall have effect subject to the following modification, namely the value of the policy shall be computed and approved by an actuary in accordance with principles which take account of the amendment and which are approved by the Commissioner.