What is IPOD's other capacity?

My cousin just formated his laptop so when he connected his ipod with newly installed itunes on his laptop, his music library was empty
well…he synced his ipod by mistake and now everything in his ipod is gone…..now here is the real problem!!!!
it’s annoying but not a problem to create new music play list and sync on his ipod but when he sync back his ipod he had his ipod filled up with “other ” (7.2GB out of 16GB)..WTF….erased browser’s history, cookies, and so on(no contract, no email account ) but still no luck
does anyone know how to erase this ‘other’ capacity on ipod??
THANKS!!!