Forget the above question.
After using Disk Management I found that the usb memory stick was partitioned and then after Googling "how to delete a usb memory stick partition" I found the following -
How to delete a partition on a usb stick<br>
which explains the use of diskpart
I now have my 64gb usb memory stick with 62.4GB free.
I recently used a 64GB usb memory stick to make a backup of the factory default of my Acer laptop directly after building the (Windows 10) system which is stored on a partition on the built in SSD drive.
The backup failed due to a problem writing to the usb memory stick. When I checked what had been written to the usb stick it showed that it's capacity was 31.9GB instead of 59.92 (or whatever the capacity of a 64GB memory stick is).
I tried formatting the memory stick but it still shows 31.9GB.
Could the backup have created a hidden partition taking up the missing space? How do I find it and remove it?
Thanks

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