My Ipad says i'm taking up 27.72 GB of storage, when I'm actually taking up much less.

I have deleted so much from this storage page, but realized it didn't matter anyways because nothing that I could delete would make up for the amount of storage the Ipad says I need. If I deleted everything from stoarge, it wouldn't even be close to the amount I need for the software update. Why is the Ipad doing this? It makes no sense and seems like a huge error on Apples part.