Why does an app say 480mb in itunes but 798mb on my memory usage?

[therealriley]

Hi all I have noticed this with many apps, I just wondered why.
For instance, I have downloaded six guns months ago, and I have been updating it since.Could this be why?
When I go to the app store it is 480mb to download, then I go to settings>general>usage where it shows as 798mb?
If I deleted the app and download it again would it stay at 480mb?
I know there may be game saves but would these nearly double the mb used for this app?

I just wondered myself, and was interested to know if anyone can shed some light or has a similar problem?
Many thanks

 

[Pocobear]

Compression / Expansion

The files are compressed when downloaded, and expanded when put on the iPhone. Therefore 480mb becomes 799mb.