有话则长无话则短

有话则长，无话则短:

Literally means:

speak to the point and waste no time

Actually means:

If you have got something to say, take your time and say it; if you don't have anything to say, be brief. This sentence is often used before a group discussion as a requirement of or suggestion for the speakers.

如有话要说，就讲的时间长一点；如没有话要说，就讲的时间短一点。常用在集体讨论发言前，表示对发言的要求。