I'm not sure what's causing what you're seeing, but you can book the 11th and 12th for around $105/night as single nights. The website won't allow the 13th to be booked as a single, in fact the 13th, 14th and 15th are not showing available as single nights. Maybe there is a large group reserved around that time that the app/website is having trouble working with your three night request. If you're set on trying to stay here, I would book the 11th and 12th as single nights and keep checking on the 13th. I'd also have an alternative booked somewhere else paying attention to cancellation policies for both.