The disk space becomes smaller after being created.

After the USB flash drive is created, the space becomes smaller and you can find it online. It is really effective and you can add it to your favorites for backup.

Diskpart press enter (run diskpart)
List disk press enter (list the hard disk list of the computer)
Let's see which one your USB flash drive is. Select disk X and press Enter. X is your USB flash drive number (don't get your hard drive !!)
Clean press enter (the above operation is to cancel the original partition of the USB flash drive and change it to an unpartitioned status again)
Now, exit this command line and go to Microsoft's disk management tool (right-click my computer-Manage-disk management). Then you can use this graphical management tool, create a simple volume or something (equivalent to re-partitioning and formatting)

The disk space becomes smaller after being created.