All the important statistics about the Google Customer Reviews program is available within your Merchant Center. 
Click here to reach to this important data in your Google Merchant Center.
All these lines are updated on weekly basis. If you are signing up fresh for this program, data takes up to 7 days to get reflected in the first graph of Survey Opt-ins Received.
If Survey Opt-ins received graph line is staying above zero consistently every week, then integration is perfect and the app is doing its job. 

This graph is of Survey Responses (i.e. Reviews) received.
You can count the total number of reviews received in the last 12 months from here. If weekly average of  the reviews received is more than 3,  you are likely to  get your store's Google Customer Reviews Badge.
If its average is less than 3 per week, we suggest you to either add another service of Seller Ratings Listed here or remove the app as it will not help you cross the magical number of 150 reviews in the last 12 months. 

Once your store has crossed 150 reviews in the 12 months, you will start seeing changes in these two graphs;
1- Overall seller ratings and
2- Number of reviews for overall seller rating. Now you are all set.