7 If the age of the insured is understated in an application for an insurance contract, the amount payable under that contract shall be the amount that bears the same ratio to the sum assured that the premium proper to the age stated of the insured bears to the premium proper to the actual age of the insured, the stated age and the actual age being both taken as at the date of the contract; the premium proper herein referred to is the net annual premium shown by the mortality table mentioned in section 4, the rate of interest being six per cent as therein mentioned.