Server response time
This is the amount of time it takes for a server to provide its initial response to a user's operation request. Often servers will respond with some information quickly, before all the information is ready for delivery. Together with the server think time, the server response time sums to the overall server time. Note that if there was no think time recorded for the opration, it equals the server time.
Server think time
The time that elapsed between the moment the server received the request for the Base Page, and the time the server fully composed the response. Depending on the nature of the request, Application Servers in the Data Center may be involved to produce the content. In such a case, this additional time will be reflected in the Server Think Time metric.
Notice that the chart is rendered in the smart mode (hint: annotation under the section title) and the values you see in the tooltip represent the value of the metric and, in the brackets, the value as presented at the chart. In the upcoming release 2017 May you will be able to interact with such a chart and reset that smart zoom.