It's basically a css print file, which includes a lot of css properties that are not built in browsers yet, with a preview you can see on screen.
print is just another aspect of responsive web design. And paged.js add the possibility to add things that the paper need and the browser don't (page number, cross rereferences, running-head, etc.)
It's definitely made to print books and pages from the web. You can preview in a browser, but that's not the goal. It's a polyfill for CSS properties made for print.
Although, you can't tell for sure what people want to do with tools and library right? :)
Reset page number using counter is working: https://codepen.io/julientaq/details/MWammZV
The property needs to be set to the element, and not to the @page.
But we may have missed a bug though, so i’ll be happy to check your code.