Note also that the line breaks are chosen by a human, and if you look at the bottom right corner of some of the images you can see random-looking digits that do

Note also that the line breaks are chosen by a human, and if you look at the bottom right corner of some of the images you can see random-looking digits that don't contribute to the image, but do contribute to the "primeness". There's the actual size of the search space, the rest of it is just picked to look that way. It's still a huge space and doesn't discount the effort of finding candidates and checking them, but it does demystify the image a bit.