The work/rest ratio is the amount of time for your sprint is the amount of rest you get.
example..
If you do the half mile in 3 minutes you get 3 minutes of rest when the ratio is 1 to 1, if the ratio is 1 to 2 you would get six minutes rest time, and so on.
The rest time is spent walking not stopping and resting.
Not sure what the differences are between one routine and another, just the progression of the workouts I guess.