Hi Dylan,
The xPath you are using is not correct. I think it should be $Booking/Bookingsystem.Booking_Timeslot/Bookingsystem.Booking/Date.
Try setting a '/’ after booking_timslot and pressing control + space. This will give suggested possibilities and will guide you.
Hope this helps!
Use Ctrl+Space to have autocompletion help you out:
You will find that it autocompletes to “Booking”
Again add “/’ and Ctrl-Space might suggest “Booking.createdDate” if you have set that tickmark at entity Booking.