When a person has acquired by gift property located outside the area where this Act is enforced, if tax equivalent to gift tax has been imposed on that property under the laws and regulations of that place, the amount of gift tax to be paid by the person who acquired that property is the balance obtained by deducting an amount equivalent to the amount of tax so imposed from the amount calculated pursuant to the provisions of the preceding Article or Article 21-13; provided, however, that if the amount to be deducted exceeds the amount obtained by multiplying the amount calculated for that person pursuant to those provisions by the proportion that the value of that property represents of the value of the property included in the taxable value for gift tax for the year in which the date on which that property was acquired falls, that deduction is not made for the portion exceeding that amount.