In the cases listed in the items of Article 15, paragraph (2), where it is found that including the number of adopted children specified in each of those items in the number of heirs referred to in that paragraph would result in an unreasonable reduction of the burden of inheritance tax, the district director may, upon making a reassessment or determination of inheritance tax, as the district director finds appropriate, calculate the taxable value for inheritance tax (where Article 19 or Articles 21-14 through 21-18 apply, the amount deemed to be the taxable value for inheritance tax pursuant to those provisions) and the amount of inheritance tax without including the number of those adopted children in the number of those heirs.