In that quote in question, he rated himself "a 6.9". Which, if you read the relevant section of The God Delusion, a 7 means "I know for a fact that no gods exist".
In other words, he is rather thoroughly convinced that no gods exist, and lives his life as if no gods exist, and only extremely compelling evidence would convince him otherwise. As a man of reason, he acknowledges that a god is possible, but unfathomably unlikely.