Ultra Fit USB 3.0 128gb, 4gb missing from drive

After plugging the USB drive into my computer, I noticed that the total available space is 115gb.  I know that I won’t get 128gb showing (I’m quite familiar with computers, thank you), however another 128gb USB drive that I got yields 119gb of space.  Even doing the math shows I should be getting 119gb of space.

Is there a hidden ‘partition’ of sorts that is taking up the additional space?  If so, is there a way to recover that missing space?  I know that with the U3 drives, there was a way to disable the built-in security to turn it into a regular flash drive.  I’m wondering if there is something similar going on here, where there is something extra that is intended to be a feature that some may appreciate and make use of, but could be uninstalled to add to the rest of the flash drive.

I am also wondering, regardless of if the space can be recovered or not, what is it used/reserved for?  I have a few SanDisk products and am aware of the quality provided, so I don’t believe this to be a defect, which leads me to believe that it’s by design.  So I’m wondering what the purpose is (and as stated above, how to recover the missing space).

The Ultra Fit have serious heat dissipation problems. I bought half a dozen 32 Gb models and half of them had less storage capacity. It is not hidden partitions, it is fried memory cells. I just wrote a post about them frying the USB ports of two of my computers. Beware this particular model: such a nice idea, but such a poor implementation.