Some dates on your booking calendar show green even though a guest cannot start a booking on them.
Why this happens. The calendar colors a date red only when the night itself is taken or blocked in your PMS. A green date means that night is open. Some open nights still cannot start a booking, and they stay green on purpose. These include nights in a gap too short for your minimum-stay rule, and nights your PMS closes to new arrivals (for example, a turnover or check-in-day rule). Many of these nights can still be sold as the middle of a longer stay that starts earlier, so showing them red would hide inventory guests can actually book.
What your guests see. When a guest selects a range that breaks a rule, the calendar blocks the selection and shows the reason, such as the required minimum number of nights.
When a green date looks wrong. If you see a green date that your PMS shows as occupied or blocked, that is a sync question. Send the specific date and property to support so they can trace it against the data your PMS is sending.