@Darius86I simulated a few bookings for varying dates and all looked pretty normal, price wise. You have reasonable weekly and monthly discounts set. Check the discount section in your listing editor for any custom prices for certain time periods.
If this was instant booked, you can use a penalty free cancellation on it. Then turn off I B until you get it sorted.
@Darius86 once you have cancelled the booking you will probably find there is a special weekly price applied to that week. It is either a system glitch or you have put in a price thinking it is a price per night when actually it is a price per week.