It shouldn't be anything like that size unless it has an awful lot of extras added to the package you've found. I'm wondering if it may include XBMC, other optional apps and tools, maybe a skins library too.
If you can look in your download's folder/sub-folders and tell us exactly what's there and using up all that space it should be helpful.
Sorry to bring this up, I'm a little OCD about it, but I'd like to see a lead given here in the standardisation of the way size units are written. When I started in gaming and going online it confused the hell out of me when people started talking about 8mb memory cards and 2MB internet connection speeds in the days when 1Mb/s was the norm.
As for Heimdall's posts upper case 'B' should be used for bytes to distinguish it from lower case 'b' used for bits. The multiplier is also normally written in upper case too ie. KB - Kilobytes, MB - Megabytes, GB - Gigabytes etc. It is how modded Xbox dashboard presents file/folder sizes too so isn't it a good idea to keep it consistent?