The Quality Filter uses lots of high-end algorithms to evaluate all the mentions through a curation process. You'll see fewer, but more relevant mentions.
A quality mention is considered to be a mention that is from a reputable domain and/or has social shares and traffic data. It is a mix of metrics that we use in order to qualify a mention as being low quality or not.
Switch ON the Quality Filter if you want to curate your mentions.
As quality over quantity is not always the case, you can choose to switch the Quality filter OFF, and receive all the mentions available on the world wide web.
Also you should know that Quick Research Tool returns also the low quality mentions.