It really depends on how much bud, how much air, how dry your environment, how wet the bud is when it goes in. Better to judge it by the uniformity of the moisture in the bud. Properly cured bud will seem completely dry in almost all regards, the main way you can tell it's not really dry is that it won't crumble when you squeeze it gently. How dry is really a matter of taste, but the key to curing in my mind is the uniformity of the moisture left.