The FAA has already published clarification - I posted a copy of it a few pages back. They say that your 10 hours of rest must provide an opportunity to get 8 hours of uninterrupted SLEEP - weather or not you actually need that much is up to you, but the opportunity must still be there. As others have said, it's essentially impossible to get 8 hours of sleep when you only have 8 hours behind the door. So, if circumstances resulted in you only having 8 hours behind the door (rooms not ready, transportation issues, etc.) and you accepted it, you are essentially in violation of the FAR since there is literally no way that you had an opportunity for 8 hours of uninterrupted SLEEP.