Cardio and C25K

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I am on week two of C25K and I know that the 20 or so minutes of running is not enough cardio if someone is trying to lose weight. In order to increase the workout, I add on an extra twentwy to twenty five minutes.

My question to you is, should I be moving up to the next level if I am doing that or can I continue this way and move up to the next level and the end of the week?