Sentence:  It is suggested that Rule VIII (c) requires that the drivers be on the track 5 minutes before <WSD>off time</WSD>, not post time, and that since <WSD>off time</WSD> can not be known until the race actually starts, the rule is meaningless. 
Meaning of the word marked with <WSD> tags:  The point in time when the official starter signals that a race begins, as distinct from the time the race is scheduled to start (post time).