What's the difference between day 3 and day 4?

In day 3 we make one superread/dip trip through book in 30 min?

In day 4 we make multiple superread/dip trip through book in 30 min?
What is mean than "at a pace that will get you through the book by the end of the session"?
One or multiple superread/dip trip through book in 30 min?