Spotify storage space depends on how much capacity your iPod touch has. (8 GB, 16 GB, 32 GB, etc...) Storage space also depends on how full the drive in your iPod is. If you have lots of apps, it means you will have less storage for Spotify. If you want to offline sync lots of music, it means you will need to make sure your iPod has enough space. iTunes and the "usage" screen in the iPod settings should help you keep track of storage space.
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