The KIND bar company recently launched KIND bar Thins with the intent to reach consumers who may have avoided snack bars in the past due to the relatively high calorie content. The sales for this new product reached 500,000 units in the first year, which can be compared to the sales of the traditional Kind Bar which reached 2 million units. However, the cannibalization rate was 25 percent. Please explain, in one sentence, what the cannibalization rate represents, and calculate the cannibalized volume in this scenario.