In other words, the strategy of Rules are applied for each Rule Set instead of for all active Rule Sets.
Use the Rule Set Overview Panel to select a strategy for a Rule Set.
When you are creating Rules for event type MSG for multiline WTOs (MLWTOs) by specifying MLWTO Minor = ALL or MLWTO Minor = SINGLE, the strategy of ALL and FIRST works differently.
For these Rules, even when you specify FIRST, multiple Rules might fire because when the Rule Processor searches for Rules that match selection criteria you have specified, the Rule Sets are scanned for a Rule for a single WTO (where no values is specified in the MLWTO Minor field), a MLWTO Rule with MLWTO Minor = ALL specified, and a MLWTO Rule with MLWTO Minor = SINGLE specified.
When you add Rules for MLWTO messages, you should try to ensure that there might be more than one Rule that matches the selection criteria you choose. In addition, if you place a Rule with MLWTO Minor = ALL specified before a Rule for the same message with MLWTO Minor = SINGLE does not prevent the second Rule from firing