My storage on iPad doesn't add up I can't understand what's taking all my storage as the apps listed don't add up and I don't download videos or music etc.
My iPad says I've used 12.2GB with 209MB available yet when I added everything up my total usage was 8GB. CONFUSED
Most likely it's the operating system, in this case, iOS. The operating system needs a certain amount of space on the iPad.

In this way, you don't get the amount of storage that you pay for, since iOS tends to usually take up anywhere from 1 to 4 GB of storage, depending on which version you're running.