Need help understanding ipad storage. [View all]

I have an ipad Air with 16 GB. Each time I get a notification there is new software to download, I have to delete apps to free up space to download the update.

I added up all the apps that I currently have on the ipad and it totals 3.12 GB's. The system is another 8.43 GB's for a total of 11.55 GB's.

Shouldn't that mean I have 4.45 GB's available?

I'm at a point now where I'm deleting apps that I use frequently.

Am I understanding this correctly? Where is the other 4.45 GB's?

When the "About" screen shows - songs 55 - photos 203 - videos 6, is that KBs/MBs, or just the number of items?



Thanks in advance for your help. I just don't see how I'm using 16GB of storage.