Hi there, I don’t really get why I can pick a date but it displays as not available?

https://poddokyasto.com/baksel/testbaksel/

https://www.loom.com/share/3e76b0cc1e1c4265b273f0b219a50668?sid=3d8d5f1c-8e0f-4b39-9d2c-a8e72af6387b