It is understood that for the computation of the reduction mentioned in paragraph 2 of Article 24 of the Convention, the items of property referred to in paragraph 1 of Article 23 of the Convention shall be taken into account for the value thereof reduced by the value of the debts secured by mortgage on that property and the items of property referred to in paragraph 2 of Article 23 of the Convention shall be taken into account for the value thereof reduced by the value of the debts pertaining to the permanent establishment or fixed base.