The difference for aggri_98, aggri_99 and do_aggri

Hi, experts

what is the difference for mdp_matrix column aggri_98, aggri_99 and do_aggri, from imp guide, all used to specifies whether to perform aggregation on this item-location combination. How engine will consider if I set aggri_98 to 1 and do_aggri to 0. In another word, if all used for indicate aggregation or not, who will take first priority, thanks a lot