Generally, after the USB flash drive startup disk is completed, the part made into the startup disk will be hidden, that is, hidden after partition. Your USB flash drive surface will also look much smaller. Often an 8G USB flash drive may be half or even gone after the system disk is completed.
Because of this, you can't see anything.
None of this matters. Just use it directly. After that, it's not needed. I can restore it.
I don't know the rest. Rubik's Cube Optimizer can really restore U disk space. You can try.