That is the average breathing rate. Try if for your self.
I came across a study "The physiological effects of slow breathing in the healthy human" that shows how 6 breaths per minute is basically an optimal rate for breathing. That would look something like the video below.
By slowing our breathing even further and prolonging the exhalation two things usually happen in our body. We start accumulating CO2 and lowering our heart rate. When we slow our breathing cycle we have to increase our tidal volume. Try the breathing rhythm below to see how it feels.
All of the above is explained in more detail in the document Slow Breathing hand out (PDF)
I'm not a scientist so the document might have flaws and errors but it does give a good basic understanding how breathing affects our bodies.