Why do I keep running out of storage?

[AC Question]

I have a Samsung Galaxy 4 with 16 GB of memory but I keep getting messages that I don't have enough memory left. My emails won't download and my updates won't run because of this. When I go to "Setting" and "Storage" the device memory bar (color coded bar) shows that I should have at least 25% of storage left by the chart but when I scroll down my "Available Space" only shows 475 MB. These 2 items don't match up from what is shows and what it says. I've taken my phone to Best Buy many times to the Samsung counter many times and they can't even figure it out. One guy said something must be "hidden" that we can't see that's taking up all the space but of course he couldn't find or fix it. Any ideas what can be causing this? I took all my photos off except for what is in my Google account and only have 2 games and no other installed apps other than what came with the phone.

 

[MindyMac3]

Did you ever find out anything about this? I keep getting a "no available space to download" message for an AT&T software update. I have deleted cached files. When I look at Settings / Storage, I see that I have 16.82GB of available space on my phone and 19.89 GB of space on my SD card. I have removed most of my pictures and while I do have some apps (Weight Watchers, Netflix, Pandora), I have removed any that I don't use. What gives? Any ideas? Thanks.

P.S. I have a Note 4 and its Android version is 5.0.1.