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