The winner is the person with the quickest time from the green light to the traps. The ET is your time from when you start until the traps.
For instance, you run a 10.00 with a perfect .500 reaction. I run a 9.5 with a 1.0 reaction. I takes both of us exactly 10 seconds to reach the traps from the start of the grren light, therefore it is a tie.