"From now on, we announce tasks of mechanical engineering review for the Unit 21 expedition members of the remote education university." North Korea's state-run Pyongyang Radio said at 12:15 a.m. "Number 69 on page 602, number 79 on page 133, number 18 on page 216." A total of 70 sets of such five-digit numbers were read out twice.The North resumed the Cold-War era type broadcast in June of last year amid escalating tensions with the South. Many believe them real clandestine orders.
Others believe because the North Koreans have been isolated from the rest of the world for so long, and their only state approved joke book so old, to save time in the telling them they just refer to them by number. The DPRK had previously suspended such radio broadcasts years earlier when it's believed their vacuum tube burned out.