28 trainees with CTC, and probably 12 with CEFA. Wizz Air first said they are looking for up to 40 trainees in the first year. Also on the CEFA website it says they have the capacity to train 12 persons.
As for the Wizz Air acting as a guarantor, that is the idea of offering you that conditional contract of employment when you start your training, that way you can borrow the needed money. As previously said, they are still talking to the banks, more information will be released soon.
But indeed, you must know the salary first before signing any contract so you can plan if you can pay the money back from your salary or no.
Another important point is there will be assessments centers in Hungary, Poland, Romania and UK.