460kB is about right for the game state. Mine is 480kB, and apparently it grows with player level.
On iOS, I don’t see this download if the app stays near the top of my app pile. It’s only if I load up a few other apps and push it out of memory that I get the splash screens and the download. Is this the same on Android?
For further explanation, the game stores its data on the servers to prevent hacking and other kinds of cheating. We had a discussion about this in the beta forum. The 480kB I am seeing is vastly better than the 2.8MB it was in 3.0! This is a big improvement by the dev team, especially for people like you and me who watch our cellular data usage.