pro-rating a Kindle Fire return

[ShaggyKids]

Hi there,

I'm seriously considering returning my Kindle Fire and purchasing the Nexus 7 tablet instead. My Kindle is not still unsealed in the box but instead has been put in use (although not excessively cuz I don't have time for excessive) so different than what I understood (without checking for sure) looks like they'd pro-rate my return. I am still within the first 30 days - it was purchased June 22 and took nearly a week to get here. Just wondering if anyone knows how much $ I'd lose if I do this? I purchased it directly through Amazon and now wishing I'd gone the Walmart route.

Thanks!