"Quanto menos usuários o site tiver, menos ele vai ganhar com publicidade."
Basically "the less visitor you have to your site, the less you earn money/revenue (online)."
earn from advertisers or from affiliate markerting, for example. Or even selling your own product/good/service.
Anyway, there´s a little bit of "chicken-egg" dillema here, because if you go overboard, by monetizing your blog/site and not creating helpful content, good user-friendly experience, you end up getting "hit-and-go" visitors (they don´t come back).
When you marginalize your audience (perhaps not trying to attract the user/visitor but rather the advertiser), the result -ironically - is that you don´t attract the audience you want and need!