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XX% caloric restriction means reducing your BMR (Basal Metabolic Rate) by the XX% amount. BMR is basically the minimum calories your body needs to maintain all its natural process. So, if you do nothing at all in a day, your body will burn the calories equivalent to your BMR. This article details how you can calculate it.
So if you're using a program that requires 30% calorie reduction and your BMR is 2000, your daily calorie intake has to be 1400. If you're active, the total calories your body uses will increase, which will lead to a higher calorie deficit. That's basically how weight-loss through dieting works.