Right.
Yeah , so these are arbitrary , assigned by a program , not  not by a user. So you have a whole bunch of those. And then somewhere la further down you might have something like an utterance tag which has " start equals T - seventeen , end equals T - eighteen ". So what that 's saying is , we know it starts at this particular time. We don't know when it ends.
OK.
Right ? But it ends at this T - eighteen , which may be somewhere else. We say there 's another utterance. We don't know what the t time actually is but we know that it 's the same time as this end time.