For testing purpose, they generate only 120 alerts every day. One full time fraud prevention analyst should be able to handle the volume. Within a week, $55K of fraud attempts have been denied exclusively due to these new rules. Two very experienced analysts enthusiastically told me that they like the rules.
These rules are designed to target the fraudulent transactions at historically risky retailers, from possibly compromised cards, with high transaction amount against card balance, etc.
There rules are completely transparent and are standard database SQL statements.