Bought used iPod and it's taking 21 hours to do a software update. Surely this is too long!

I bought a used iPod Touch 4th generation which I later found still had previous owner's details left on. Instead of doing a restore to factory settings immediately, I put in my own Apple ID etc. When I tried a restore it wanted a passcode. Contacted previous owner who said she'd never had a passcode on it. Anyway, I put the iPod in DFU mode and set it to restore and update to next ios. However, it's taking 21 hours to do! Is this right?

Thanks for any help.