Order: rules are checked from the top of the list. Change the order with Move up and Move down. When several rules match, the strictest decision wins (Blocked, then quarantine, then inbox with a warning, then inbox), their added scores count together, and the quietest notification setting wins.
Stop checking other rules after this one: when this rule matches, the rules below it aren't checked. That's how you make an exception: a rule at the top that delivers messages to your inbox, with this option on, wins over a broader blocking rule below it. For example "always deliver messages from my bank's sender name". Use it only for senders you're sure about, since such a rule lets their messages through.
Re-checking quarantine: after saving a rule, 1krBlocker asks Re-check quarantined messages? Apply this rule to messages already in quarantine? Only their risk labels change; nothing is moved.
To see why a particular message matched, open its Why? screen: the Your rules group names the rule.