486.5. For the purposes of section 486.4, the portion of the original amount that was included in computing the income of the recipient or that was not deductible in computing the income of the recipient is the amount that would be included in computing the income of the recipient under section 89 or that would not be deductible in computing the income of the recipient under section 144, if the original amount were equal to the eligible portion of the specified amount, determined under section 486.9.