Wrong, you can not be scheduled over 8 hours. If your current schedule is 7:53 minutes of block and you fly 8:49 then this is legal. But, if you have flown 5 hours and you have 3.5 hours of flying left on your original schedule (total of 8.5 hours); and you get reflowed to a schedule that is 3.5 hours then it is illegal. If they revise your schedule then the 8 hour rule must be reapplied and the above example will show you scheduled for 8.5 hours after the reflow (illegal).

So, scheduled 7:53 and you fly 8.5 then legal. Scheduled 7:53 and reflowed to 8.5 then illegal. "Legal to start, then legal to finished," regardless of actual flight time for the day.