Attributes with unary operators or custom rollups should have full aggregation usage
This rule analyzes aggregation designs to see whether attributes that use unary operators or custom rollups have their AggregationUsage property set to Full.
Best Practices Recommendations
For best performance, you should typically set the AggregationUsage property to Full for attributes that have a unary operator or custom rollup defined. In addition, for parent-child dimensions, if the parent attribute has a unary operator or custom rollup defined, you should set the AggregationUsage property of the parent attribute to Full.