Where an order is made in relation to the member spouse's retirement benefit, and retirement benefit is calculated on a defined benefit basis, the retirement benefit payable to or in respect of the member spouse from that pension scheme shall be reduced by whichever of the following is applicable:

(a) the designated benefit payable from that pension scheme pursuant to the order, or

(b) designated benefit that would have been payable from that pension scheme pursuant to the order had it not been for -

(i) the application of a transfer amount pursuant to section 12 (5) or section 12 (8) of the Act of 1995 or section 17 (5) or section 17 (8) of the Act of 1996

(ii) a payment pursuant to section 12 (9) or section 12 (10) of the Act of 1995 or section 17 (9) or section 17 (10) of the Act of 1996