For most of my life, banks ran an algorithm on overdrafting accounts so that charges would clear in whatever order triggered overdraft protection the most times. It was an open secret, then it came out and companies tried to insist they could do whatever they wanted.
Lots of real world cases of a single unexpected charge coming in and clearing a full day earlier than expected so a bunch of small charges (a pack of chewing gum) would each trigger the fee. $100 total charges, $500+ in overdraft fees.