15. The Minister shall determine the sum that may be deducted at source having regard to the support payments to be made, up to the portion that is seizable for support debts as determined pursuant to the second paragraph of article 553 of the Code of Civil Procedure (chapter C-25). Arrears in support payments and fees, if any, may be included in that sum, in such proportion as the Minister determines. For the purpose of determining that sum, the amounts referred to in subparagraphs 2 to 4 of the first paragraph of section 11 are deemed to be salary.