The app stores every image, every piece of data you ever used I believe. At one point I also had over 2GB of data on my iOS app. So I deleted it, re-installed it and viola...cleared up a ton of space. The UA app is an awful iOS "citizen" and should be clearing its cache of useless images, old data, etc.
I probably last did this a couple of months ago, I'm traveling way less than normal (figure about 50%) and I'm back up to 1.35GB of documents & data already.
-RM