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if the ipod needs to go in to apple store simply restore to original firmware and they are non the wiser and still under warranty
 
This has been posted many, many times already (in the past month alone). Yes, it's safe. Jailbreaking can be reversed, it does not cause any permanent damage. For the last question that you asked, "what does that mean," the answer is that it is used to put your iPod touch back to the old firmware (before jailbreaking).
 
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