This is a very important guideline for very serious people. It's all about being on time and not being late. Like, ever.
Arrive precisely at 5:00 PM for the meeting. If you're early, you're wasting company resources by sitting idle. If you're late, you're wasting your own time by being fashionably late.
This guideline is not actually enforceable. But you should probably still follow it, just in case.