Is my summary of the rulings on menstruation correct, and is it valid to consider the brownish discharge (Kudra) that follows menstrual blood on the sixteenth day as istihadah (non-menstrual bleeding) if the blood that preceded it during the period of less than purity (less than the minimum interval of purity) was not considered menstruation, or is it considered menstruation in this case? And do I pray after a day and a night have passed since dryness, or do I perform ghusl (ritual bath) and pray as soon as I feel dryness, even if only for an hour? And is a woman punished if she makes a mistake in estimating her menstruation or purity? And how can one reconcile between the different madhabs (schools of thought) regarding the ruling on blood that appears before 15 days of purity have passed?

The default rule for blood seen by a woman is that it is menstrual blood. She is not considered to be experiencing irregular bleeding (istihada) unless she sees blood at a time when it cannot be menstrual blood. The maximum duration for menstruation is fifteen days, and the minimum period of purity (tuhr) between two menstrual cycles is thirteen days. If the blood stops for less than fifteen days, then all of it is considered menstruation. If it returns after more than thirteen days, it is a new menstrual cycle. If the duration of the blood and the period of purity within it exceeds fifteen days, and there was not the minimum period of purity between them, then the woman is experiencing irregular bleeding (mustahadah). Yellowish and brownish discharges are considered menstruation during the accustomed period or if they are continuous with the blood. A woman recognizes purity by dryness or by the white discharge (al-qassah al-bayda’). She must perform ghusl immediately upon seeing one of these two signs. If a woman understands these rules, she will know when blood, yellowish, or brownish discharges are menstruation and when they are irregular bleeding. There is no sin upon one who refrained from prayer or prayed based on her assumption that her condition was correct, and then it turned out otherwise. However, one who refrained from prayer assuming she was menstruating must make up those prayers. A woman must follow the opinion of a scholar whom she trusts.