The numbers roughly correspond to the width of wires in the circuits, but the number of circuits you can fit per unit area depends on the square of that number so going from 7nm to 5nm roughly doubles density. The first microprocessor[1] was around 10,000nm so we're approaching 5,000x thinner wires or almost 25 million times more circuits (the latest Apple M1[2] is at 5nm have about 8,000,000x as many transistors as the 4004).

[1] https://www.intel.com/content/www/us/en/history/museum-story... [2] https://www.apple.com/newsroom/2020/11/apple-unleashes-m1/