My understanding is that 70 million was indeed chosen arbitrarily, but it is large enough to make the proof work without too much extra work. The "2022" number

My understanding is that 70 million was indeed chosen arbitrarily, but it is large enough to make the proof work without too much extra work. The "2022" number in the recent claimed proof might also be in this vein, i.e., there is nothing special about it, it's just a number large enough to make the proof succeed relatively comfortably, and probably also a play on the current year.