The first offer (16,90) is a seat in a six place seating compartment, the second one (66,90) a place in a six place couchette compartment, the third one (311,90) is a complete private sleeper compartment. 

It would have been better to do the booking with ÖBB (nightjet) direct. Cheaper (no booking fee), more choices and you do see the location of seat or bed you do get and there are pictures, too.

Thank you for letting me know!

But I think I'll probably have to use the ticket I've booked now since there are no seats left.

Can you tell me which seat numbers and which represent the train compartment in the table below?

Coach 422

Berth 83 (middle couchette)

422 is the number of the carriage. 

The compartments are not numbered per se. But your place is in the 8th compartment (of 9).

83 is the number of the bed. As you may see, it's in the middle of 3 on one side of the compartment. 

With ÖBB, it's still possible to book e.g. the lower bed in this compartment so it doesn't look completely sold out. But it's not possible to change the reservation without a fee anyway.