Just an interesting quick check of numbers...
According to
U.S. Bureau of the Census, the population of the world is currently some 6.294 billion people. If .1% of those don't accept the Matrix as a reality, then that means about 6.294 million people are going to get ejected from it, hopefully migrating to Zion. Very generously assuming that about half the people ejected from the Matrix are fortunate enough to be rescued and rehabilitated by the Resistance or otherwise survive the dangers of being in a barren wasteland with extreme atrophy caused by never using any of their muscles before and still somehow manage to find their way to Zion, that places the population of Zion at just over 3 million people. Comparatively, the
population of New York City is around 8 million people. That makes Zion a relatively small city... kinda depressing for the last of the human race.
Of course if the Machines know all this, why the Machine don't just take the easy way out and put some shredders on the other end of the ejection chutes so that if a person WAS ejected from the Matrix, he wouldn't even have a chance to be rescued by the Resistance and instead would be just fed back into the system, I don't know....