[Koha] Broowsing by subject - number of biblio records

Browsing by subject allows us to find bib records using any authority list wich seems very useful. But I have seen several KOHA 3.0 demos where the page Authority search results allways display 0 biblio records. I have tested and did some links between biblio and authority but it never changes. can anyone help to solve this question? Does we need to run any script? Thanks, Rafael Antonio