The item Reorder Point is not a fixed value.  It is dynamically calculated by the program whenever an item’s monthly demand rate, Lead Days, or Job Days value is changed.  It is a trigger point for MRP generation that has no relationship to a stocking level.  In fact, the Reorder Point amount has no inherent meaning unless it is in context with the item’s other settings.  

If you have been using the Reorder Point as a target stocking level for manual planning, which has never been a recommended practice, this is no longer possible because it is now a calculated value rather than a fixed entry field.