TT #9 · Parshas Tazria · Aliyah 1 · Passuk 2
English: Speak to the Israelite people thus: When a woman at childbirth bears a male, she shall be impure seven days; she shall be impure as at the time of her condition of menstrual separation.
Chabad.org — Chumash, English translation + Rashi for Vayikra 12:2
Torah Temimah cites Niddah 31b.
English: “She shall be impure seven days” means that she counts seven days for the last child.
Sequential counting
Where childbirths are close together, the seven-day childbirth-impurity period is reckoned from the latest birth.