WO Age Calculation in the "WIP Inventory Value Report"

Summary: How is the WO Age Calculated in the Oracle Fusion Out of the Box "WIP Inventory Value Report" which provides information for reviewing and reconciling Work-in-Process Inventory Value.

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We use the WIP Inventory Value Report for Work Order Aging Analyses and trying to understand how the WO age in UOM "Days" is calculated as it seems to be more than just the number of Days since the WO was released. It appears to take into account most recent transaction date and operation state. I need to be able to clearly define this metric to the business users. I am unable to find anything in the documentation.