In order to be able to manage the HostelWorld non-refundable rate from the system, it has to be correctly set up in your backoffice.
In the rates configuration in your backoffice click on Add Non-refundable rate button.
Make sure that the rate is active, choose the Amount option and click on Save:
When the rate is CORRECTLY set up, it will appear in HostelWorld mapping this way and it can be mapped:
If you set up the rate to be derived in the backoffice, it will be incorrect, because you won't be able to manage the prices through FrontDesk Master.
In such cases you can't map it in the channel manager. You should live it unmapped: