I have a 4G iPod touch i jailbroke a few mimths ago running on 4.1 I believe and it's 8 gb.
The owner says that there is no disk space to put stuff onto it. But it has fewer data on it than my 8 gb does. Even deleting an app doesn't free any space. Anyone know a remedy without re jailbreaking?
Most apps are small and it may not 'register' in the giga-byte range. Some game apps are huge. Try deleting one with a lot of graphics ... like race car, shoot'em-up app types. It still might take 3 or 4 to notice a difference in the iTunes slider.
Do you have SBSettings installed? Swipe that and the second number on the right will show your available space more precisely. It will also increase when you delete something.
When all else fails, a restore will clean everything and start fresh.