When reading Plate IQ reports, it's important to understand that the Unit Price and Total Spent columns are actual numbers drawn from your invoice data. 

Item-level information on a Plate IQ report.

In contrast, the Cost Impact is a projection of how much you stand to save or lose given the item's current unit price, the timeframe you've chosen (e.g., 1 week, 1 month, or 1 year), and your usual purchasing habits. 

If any of those factors change—for example, your vendor changes the price again or you begin purchasing more or less of an item—the Cost Impact will necessarily change as well. 

Related articles:

How to Use Hot List

How to Use Spend Analysis