You can see the amount of people you have reached and how many have opened your message and replied.
You can find these performance metrics of your Engage flow on the top right part of the screen when you are in an Engage flow.
Here's what the numbers mean:
Reached: the amount of potential candidates who have received your email(s)
Opened: the amount of potential candidates who have opened one of your emails
Replied: the amount of potential candidates who have replied to one of your emails
