I think the rule is supposed to change in October and it seems you have to stay in sleeper consecutively for 8 hours.
we shall see what happens this time.
This link is the actual site that has the new rules listed.
Hope I helped some.
When they say stay in the sleeper they mean stay in the sleeper . Make a trip to the rest room or come out for any other reason and you have to start all over . Solos are better off just to log 10 hours off duty .
