Why is my "other" so big

When I see the itunes screen when my iphone is plugged in it shows that there are over 600 mb of "other" space on my iphone. i dont think there is anything else in my other besides iphone apps. when i go to the apps folder in finder there are only 214 megabytes of apps.

i understand there may be some extra space due to saving game files and what not(and all the tap tap revenge songs ive downloaded) but these shouldn't account for 400 megabytes, should they?? are apps that ive downloaded on my iphone and deleted on my iphone still there taking up space?

all i do to delete apps on my iphone is press the little X and press delete, thats the proper way, right?