@Michelle and @Danny9, I've just had this happen to me for the first time (after 15 guests). I don't understand how it could be connected to 'conversion'.
Conversion to/from what? If it were really the US$ exchange rate, the amount would be less than €1. And each booking would have resulted in my receiving varying amounts, as my guests were from a wide range of countries.
My fee is for X euros per night, and I received X euros minus €1. (The AirBnB and host fee had already been deducted.)
Just a little puzzling. I suppose I could go to the horse's mouth and ask AirBnB. 😉