When we read Deng Xiaoping's speeches, at the time he said, “I'll give you 50 to show I mean business”. He had this long-term plan that in 50 years China would develop and modernize enough to converge to the level of development of Hong Kong. That was his big idea. He also said said, “I could give you another 50”, or “We'll see where it goes”. China has not closed the door.
It came down from Deng Xiaoping as an image of a whole plan that he had for China. I don't think it was thoughtfully calculated.