@Dierdre0 Yes, 28 days (or, to be exact, 28 nights, as @Alice-and-Jeff0 pointed out) is a "month". In other words, exactly 4 weeks.
If a listing offers a weekly percentage discount but not a monthly discount, that discount will be applied for any booking more than 7 days (7 days, 9 days, 99 days if you allow 99-day bookings. However, if a listing also offers a monthly discount, it kicks in on day 28 and applies to the entirety of the booking beyond that.
I say all that because some hosts think that weekly discounts apply only to whole-week increments and that monthly discounts apply only to whole-month increments. Not true.