Is the day menstrual blood appears after midnight (12:30 or 1:00) considered the first day of menstruation, or is it the following day? And is the questioner's calculation of her menstrual days correct, or did she not become pure until the discharge appeared following the period of dryness?

If a woman has a regular menstrual cycle, she calculates it from the time she first sees blood until the corresponding time on the last day of her usual cycle. Purity is recognized by one of two signs: dryness (al-jufūf) or the white discharge (al-qaṣṣah al-bayḍā’). She must perform ghusl (ritual bath) immediately upon seeing the sign of purity, even if it occurs within her usual menstrual period. What the questioner did by performing ghusl after dryness is correct, and the white discharge she saw afterward does not invalidate it.