The way the Availability calendar works, is that when you block some days in your calendar, they are effectively made as your own booking for your own property. They will not be available to other users.
If you were using Calendar Sync, that email confirming a booking is also normal — it means a reservation from another platform (like Airbnb or Booking.com) was imported into NaturistBnB through your iCal connection.
When an iCal feed is connected, NaturistBnB reads the booked dates from your external calendar and adds them to your NaturistBnB calendar to keep everything in sync.
Because external systems don’t share guest details through iCal, the imported bookings are created under your own account — this simply blocks those dates to prevent double bookings.