Please dont mark my spelling of Summarise as incorrect. I speak English, not American
As an instruction, this seems unclear. Do they mean "write a summary", "write with haste", or "write for a short period of time"?
My reply "Write briefly" was accepted, so I would say they mean "Don't write too much - keep it short". (I suppose that would also take less time, but I didn't see that as the main focus.)