Sometimes this one is just called "Interval Max" because when it was made there were no others, so no need for the numbers. The reason that you couldn't find it is because it is bundled on the same DVD as Rhythmic Step and Maximum Intensity Cardio (2 great cardio workouts on their own!! RS is steady state step and MIC is steady, intense Hi/Lo aerobics followed by steady, intense step with some blasts at the end, but it isn't an interval workout as IMAX is).
Have fun!
Mattea