9. Beware of apps’ internal downloads
We don’t usually care how much space an app takes up for its internal downloads, the numbers you see in Manage Storage include how much the app itself takes up along with the data inside it. Some apps might be small by themselves but can store a lot of files. Such as, the Spotify app is only 56 MB, but if you have a lot of music downloaded to your phone, the app takes up an insane amount of space.
Say if you have about 800 songs downloaded, it takes up about 2 GB.To see the app size versus downloads within it just by tapping any app icon in Manage Storage.