Why do I see a second time/timer briefly displayed upon completing a call? For example, I get a call from a friend who's out of state. We talk for about 15 minutes. I hang up before she does, and when I look at the display after pressing the 'End Call' button, I have seen displayed times from 0:55 to 1:06 (only as an example, and displayed for maybe a second or 2), then the time of the entire call (e.g. 15:10).
What is this second time that is briefly displayed?