.... I'm also amazed that you got an answer.
The ice-breaker is down to you, stand there umming and ahhing thinking what to say next, and you'll be up there longer, and they will keep asking you more questions, get up there and be confident, keep speaking about your self, family, job choice, etc (there is a board with a list, work from it, but don't go down it) and you will be there a few minutes at the most,
But then, maybe you actually want to know what the run time will be, and in which case, depends, what your joining, and your age. Best advice, run so hard your breathing for air through your a$$ hole, Glencorse 1.5m is good as your turn at the half way point, so you know exactly how far you have left to go