I was intrigued by the page numbering system in this book "Making and Breaking the grid"
How could we do something like it? Is it a Link, A type of Programming?
It's a spread. Let's say Page 14 on the left and 15 on the right spread. But the two numbers are only on the right spread like 14/15.
One way to do it would be to put an other wise empty text frame on the left page and insert a frame break, then link that frame to another text frame on the right page. In the second frame add both a Previous Page and Current Page Marker.