Show all journals in the library and their number in addition to journals and their number in each category.
Users want to see the scope/size of the library. They are asking how many journals are available in total. Subject categories artificially and subjectively segment journals. They may hide some journals from the users especial in the highly interdisciplinary research. Researchers do not want to jump between multiple categories and repeat browse in each.
This is not an issue of analytics. This is common sense feature available in any search system. Users want to know whether they are entering a huge supermarket or a small convenience store. In those places they can easily see the number of aisles, their lengths and able to plan accordingly.
This feature was also requested here:
It is absolutely essential!
Next to a subject, show in parentheses the number of journals within that subject.