There are several ways to look at an item in surplus:
On hand inventory is greater than Max
Net inventory (quantity on hand + quantity in order – reserved quantity) is greater than Max
On hand inventory is greater than a number of months of annual consumption, the number of months being defined by class and by family
On hand inventory is greater than Max on hand (safety stock + economical order quantity)
All of which can be analysed by product class, product warehouse, product family.
There are ways to prevent surplus and there are exceptions report to take corrective actions.