Hi Sarah
I've got the 30 day shred and think its great, especially with it only being about 24 mins for each exercise. Like ClareyCakes says you are supposed to do 10 days on each but I also moved onto Level 2 around 7 days into it. Its surprising how quickly your stamina improves and by Day 4-5 I could manage the Level 1 all the way through without stopping and not too much out of breath. The idea is to do the 30 days for 30 continous days but I found that I was doing it around 4 days a week a could feel a difference after a couple of weeks.
Good luck with it!