The plugin (rather OK in it's basic form with content based recommendations only, not recommendations based on collaborative filtering, that needs an account) allows you to configure the size of the recommendation list, but items should not be listed if they fail to reach a certain level of relevancy.
So the relevancy rule should supersede the size-of-list rule, as listing barely relevant content is worst than not listing it.
The level of relevancy could be set from the plugin's configuration page, in close proximity with the size of the recommendation list option.
PS: The plugin's actual name is "Aliiike Recommender". The WordPress
Plugin Directory calls it "WP Recommender" and should be updated.