SLA First Reply Time & Next Reply Time

For clarification, I've created an SLA Policy and included two targets First Reply Time and Next Reply Time. Both are under Normal priority and have the same time duration (16h business).

With the requester's first comments, the policy will only run on the First Reply Time. So the SLA is timing that. Correct?

If the agent responds and then the customer responds again, the Next Reply Time Target will then activate, correct? Since the First Reply Time only measures the time between the first public comment of the requester until the first public comment of the agent. 

I just want to make sure that including two targets like this won't cause the SLA policy to become inactive.