Definition: Returns people whose active profile satisfy the User Defined Field’s Argument Value criteria on a specific target date. The argument value is the User Defined Field’s (UDF) gray number or unique identifier available on the UDF in Setup > General > User Defined Fields.
Return value: The return value is dynamic and dependent on which UDF the user supplied. For example, a String UDF will return String values, a Date UDF will return Date values, a Number UDF will return numeric values, and lastly the boolean UDF will return either True or False or both and dependent on whether the Where field in this base rule type contains limitations, such as TRUE, 2, =2, >2 and so on.
Source: Person profile tab.
Sorting: If this base rule is used for sorting in a List Target or a List, then people with a blank value sort behind the other candidates in an ascending sort; otherwise, they are preferred (sorted to the top) if the sort is descending.