Upgrade 7.9 to 8.6 Error: Not enough space available for creating required disk images in /var/lib/leapp/scratch.

I keep getting the same error message when trying to upgrade from 7.9 to 8.6. Except each time it asks for more space. I have tried running the export LEAPP_OVL_SIZE= command, but each time it asks me for more space. Now it says: "Needed 600000 MiB". How do I resolve this? Thanks.