Auditing changes to aggregate properties
The history detail for aggregate properties does not indicate changed values as it does for single-value (scalar) properties. Instead, the history details shows two entries when a value is changed: one entry about deleting the prior value and another about adding the new value.
When you create a field value rule for a message for a Page List or Page Group property, do the following steps.
For the field value rule's Applies To class, use the class of the embedded objects.
For the field value rule's Field Name (the second key part of the field value rule), match what is entered in the data transform for that property.