Too lazy to bust out PWA but my understanding (and more importantly my experience) has always been the opposite of what you just said. As in a 30 hour rest was actually 40 hours off. That could be because they assign res the day prior, so when you start rest they wouldn't have anything for you when the rest ended--I dunno. But even with yellow slips in, it always worked out to at least 40 hours between block in and sign in for next assignment.