Xavier NX no boot

I am using Ubuntu 18.04 on VirtualBox and I added 50GB from icloud through apple purchase. When I open SDK manager to start the process I have this error message (System requires up to 31GB(host) and 8GB(target) of available disk space during setup. Can you suggest a solution?
Thank you
Gregory Campbell

The 50GB is free space. The operating system itself, and the tools for flashing, consume a significant part of that space. You’ll need to start with more than 50GB to have 50GB remain.

Tip: You can run “df -H /where/ever/you/flash/from” and see how much space is consumed, and how much space remains. This should tell you approximately how much more space you need (the ext4 filesystem itself consumes some space, so if you need exactly 30GB, then you might allocate 35GB instead so that the filesystem inefficiencies can be ignored).