You need to set the number of conversions and other following parameters in regard to the Review Notifications here :
1. Enter Number of Conversions to Display : You can set the number of Google or Facebook reviews that need to be shown on your website from here.
2. Show reviews from last : You can also set the time frame of your Google or Facebook reviews for example reviews for the last 5 hours or days can be displayed.
3. Hide review if star less than : This will help in not displaying the lesser reviews or recommendations.