128GB means 100GB

If your flash drive or SSD or smartphone or whichever storage has 128GB, it realistically means 100 GB.

Not only because of reserved space, but because of those 128 GB, the end is not so useful, since you might want to put files there that are slightly larger than the remaining space, and you would like to have all those files in one location to avoid confusion and the annoyance of changing media.

 

In other words, if you would like to put 11 GB where only 10 GB are available, those 10 GB are as useless as 0 GB.