(4)Where the person accountable knows of any property which he has not included in his account because he does not know its amount or value, he may state that such property exists, but he does not know the amount or value thereof and that he undertakes, as soon as the amount and value are ascertained to bring a supplementary account thereof and to pay both the duty for which he may be liable in respect of such property and any further duty payable by reason thereof for which he may be liable in respect of the property mentioned in the original account
