@John5288 They are nights booked, not days.
It sounds as if there was a glitch, but the only way to know that is to look on your reservation to see the number of nights booked- it appears as "3 nights x $xxx". You can't say you got charged for 3 nights when you only booked two simply based on what you thought the nightly rate was.
Your reservation will show the number of nights you were charged for and a breakdown of the additional charges for cleaning fees, taxes, and Airbnb service fees.