Yes, the App helped remove much within the cache of my iPhone 5S, but it did not fix the large discrepancy that remained. Here is what solved my issue of this problem.
It all starts a few months ago when I changed internet service provider and changed my Apple Id to a new Service Provider (different email address).
When I changed my Apple ID to the new email address (Apple Id's are email addresses), I chose to save the old data on the iPhone when I changed my Apple Id to the new one. (signed out of old Apple Id and signed in with my New Apple Id) So, all data remained from the old Apple Id and was inaccessible (Many Gbytes)
I discovered this by performing a "Restore iPhone" link within iTunes on my Mac in the hopes that I could reset the Gb discrepancy. The restore process resulted in replacing my current Apple Id on my iPhone with my Old Apple Id and I was now STUCK! I could not figure out how to sign out of the Old Apple Id because I had forgotten my Old Password that was associated with that Old Apple Id and so, I could not reset or restore the iPhone. Like I said I was Stuck.
So I then researched how to reset the iPhone when logged in with an Old Apple Id for which you do not know the password. Here is the link:
If you're asked for the password to your previous Apple ID in iCloud - Apple Support
I found that I needed to add the old email address to my list of alternate email addresses (done via Mac) for the current Apple Id, after doing that, I set up the Old Email Address (Apple Id) as Primary Email Address. (There isn't a requirement to verify non existent email addresses for the short time this process is setup)
After doing this, I now associated the Old (unverified and primary) email address with my current Apple Id and was able to sign out of the iPhone using the current password I had set up with the current Apple Id.
I then signed back in with the new Apple Id (new email address) with the same current password and set the new Apple Id email address as primary and deleted the old email address.
My iPhone is now showing exactly what the Mac is displaying.
I am guessing most of you with this problem have had prior email addresses associated with prior Apple Id;s?
If this helps anyone, great!
Have a good day, 🙂
Jim