If 2 or more provisional orders in respect of a judgment debtor have been served on a garnishee, those orders have priority according to the order in which they were served, subject to the following:

(a) if 2 or more orders are served on the same day, each order has the same priority and the garnishee is to deduct one prescribed amount only and distribute that amount equally to each relevant judgment creditor;

(b) in any other case, the garnishee is to comply with any later order as if the net earnings to which that order relates were the residue of the debtor's earnings after the deduction of the prescribed amount under any earlier order.