Q: iPod Touch 4th generation -space issue

The difference between th8 GB and 6.4 is due to the iOS taking up most of the  and of how GB is advertised and used/reported.

How Mac OS X and iOS report storage capacity

You might be able to reduce the other by restoring the iPod from backup.

Well technically the reason why your ipod touch took 6.41 gb than 8 gb is because your ipod touch allready has built in apps like maps,calender,reminders and etc. I hope this helped.

and you cannot delete those built in apps, by the way.

yes it will.If you go to your computer go to itunes if you go to the bottom of the page you will see this title. It says Back up so then you have the options to back up with icloud or your computer. So then you can restore your ipod touch and you can download your music and etc again after you fully restored your ipod touch.Hoped this helped.

Well If you look on the side bar of itunes click itunes store and you can download music and it will directly go to your music library. You will have to search the music of coarse.

i think you know this but you have to pay for the music on itunes store.

well in my opinion i think  that the 8 gb ipod touch is actually 6.41 gb is because of the built in apps like maps,calenders, and etc.

Accutally no thats no the case because the built in apps and all that stuff already put on your device is the other bar on your Itunes usage. That is what i think.