Great news! Now you have to update your Availability Calendar.
The process is easy. You simply login to the Lefkada-Rentals Administration panel. Edit the rental you had the booking and select "Calendar" tab.
Then, click and drag since the "Checkin" date, to the "Checkout" date.
Then, set the status "Booked" and if you want, a daily price.
You will notice, that the "checkout" date is not calculated, as travelers always pay for Nights. So on your calendar, this day (night in fact) will remain available!
Also, on your availability calendar, the guests will see that this night is available.