God knows those to whom we intend to send our prayers. I simply add, after a relatively-short list of specific names, "and for all those for whom I generally intend to pray, for all those to whom I have offered my prayers, for all of my benefactors and friends, for all those whom I have hurt by my sins and for those who have sinned against me." I do this in the context of having offered all of my merits and prayers in general to Our Lady according to the philosophy of St. Louis de Montfort. I trust her to distribute the merits of my prayers as God would desire that they be distributed. Otherwise, one can be overwhelmed with scrupulosity and even neurosis. Plus there's the angst of trying to figure out how much to distribute to each person. This way we put the entire values of our merits, such as they are, in Our Lady's hands, to distribute accordingly. Our Blessed Mother will handle everything perfectly for us.
Of course, we don't really have any merits that aren't communicated to us from Our Lord anyway. It's like a parent who gives his kids a little allowance money, and then they save the allowance money to buy some gift for their parents. That money comes from the parents in the first place, and the parents have far more than what the kids give back, but it's all about the heart and the intent.
So one of the many secondary benefits of consecration to Our Lady is that we offload this particular worry and concern from our hearts. I ask her to distribute the merits of these prayers as SHE desires. Otherwise I can get carried away with wondering whether I should pray more for souls in Purgatory or for the conversion of sinners or for whatever else. Our Lady knows best.