What did you eyeball to get 2 GB? Remember the iOS can use up ~2 GB.
To be certain, on your iPhone go to Settings>General>Storage & iCloud Usage>(Storage)*Manage Storage and you will see a list of all the apps that are consuming some of your 12 GB. Some of them may allow you to trim down what they are consuming.
*Pick "Manage Storage" from the "Storage" portion, not the iCloud portion.
On a Mac since 1984.
Currently: 27" iMacs, Macbook Air, macOS 10.14.x,; iPhones, iPods and iPads galore!