If Boot Camp Assistant says your USB drive couldn't be created or doesn't have enough space
You might need to update your macOS or use a later edition of Windows 10.
In certain circumstances, Boot Camp Assistant might say that your bootable USB drive could not be created, or that there is not enough space available on the disk. To resolve, complete these steps:
Make sure that you're using an external USB flash drive with a storage capacity of 16GB or more.
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