Samsung Tablet A, 16GB memory full?

My Samsung Tab A (2016) shows my storage almost full, but the numbers do not come close. I've run various cleaners, deleted everything not used, put most of my files on the Cloud somewhere, and still almost 14GB are unaccounted for. My settings does not have a "storage", it has "Device Maintenance." I've found no way to clear all caches at once, so do it app by app. I have tried everything I've found on the web, various programs, still get warnings my space is running out. I almost replaced with the next model year (2019) but fear the same thing will happen. I use it as a e-reader, but all my books are in the cloud, on my SD card, or are removed from my device after reading.I rarely use it as a camera, and don't store any image I don't use. Am I spazzing for no reason? Screenshot of my "storage" tab.