Web App and AMZScout PRO Extension are separate products that complement each other perfectly.
While Web App is used to find ideas of profitable products by filtering parameters and categories, with AMZScout PRO Extension you can deeper analyze each product and niche in real-time.
Web App and AMZScout PRO Extension use different ways to collect data and to calculate it. Web App is a cloud service. The extension works with Amazon API, so it doesn't need to store data like Web App does. Moreover, the algorithm is different: Web App calculates est sales by the rank that it received during the upgrade. And AMZScout PRO Extension gathers rank for the last 30 days and calculates average rank. So estimated sales in it are based on the average rank per month.