Mismatch Percentage is the difference between how many shoppers are looking at specific models on your lot compared to how many vehicles of those same models. Mismatch percentage is always the absolute value of a number (positive number even if it is negative).
For example, if a car dealership has a total of 100 cars, and the car dealership has 10 of Car As, that means that the Inventory % is 10%.
If there are 20 out of 100 customers that want car, the Shopper % is 20%.
The Mismatch Percentage would then be 10%.