[Koha] Multiple libraries assigned to a patron

Hi all, I'm discovering the Koha library I inherited from previous admins. Since I'm a bit new to Koha administration I'd like to know if things were done the correct way. So far I saw that 7 libraries were defined but afaik patrons can be assigned to one library only. Libraries in our organization are per country but staff members are supposed to administer all of them. Is it the correct way to define different libraries but then how to assign multiple to a single patron or only one library should have been defined and then book location would be the right property/field (not sure I'm using the proper Koha terms here) to assign a book to a library? I hope I described my situation clearly. Thanks, Alex