Share your experience!
Try settings-apps-all-media storage,force stop and clear data.Restart your device and see how is the memory.Did you try to connect the device to computer and see how memory is shown?
You might have something from old apps,otherwise that doesn't make sense.Check in android-data and obb.
It might be that windows does not see all the memory or otherwise.Really awkward though,did you use some task killers or cache cleaners?
Same thing happens to me, windows always shows less memory then the phone does. Really annoying
Yeah,it might be the case like bruteoutlawz said,it happens.