This script in profile pages in Instagram. It adds a static element in the upper right corner of the page, showing how many images out of total are visible (and also as a percentage) (see screenshot in the end).
The instagram site uses single-page application workflow (i.e. the history API). Since v2016.08.02 it's no no longer needed to open a profile page in a new tab (now using the excellent library arrive.js).
Thanks a lot to wOxxOm for his valuable help in here.