Okay then, I'll tell you how I was able to get an accurate figure on my rollout...
When using your practice tree, first set it to zero rollout, and exactly 1.000 second on the delay, hit the top bulb as if you were t-braking with a delay box......you'll find your most consistent reaction to the light is the first one you see, so we'll establish your "DRT" or Driver Reaction Time, to seeing the lamp. Be comfortable with your reaction, nearly mindless, no leaning on it, or laying off of it. On average, most racers will find that DRT to be something between .170 and .220, so say you find your "spot" is .190 on the display with the settings as above. Of course they will all be redlights, don't worry about that, we are training your eye to tell a muscle to move, in a consistent manner.
Now, once you have mastered being consistent, and have your DRT number, put Zero rollout in the tree, and ZERO the delay, then hit the bottom bulb until your DRT is the same as it was off the top bulb, then you can be assured that your eye is focused on that bottom bulb well, and you are reacting to it as consistently as you do on the top bulb.
Go to the race track and test.......now you'll KNOW that you "hit" the bulb correctly, because your eyes are trained now, don't worry about whether you footbrake or release a button, you have only been training your eyes to this point.
At the track if your repeated total R/T off the bottom bulb is consistently .500 or .000, you would KNOW that your VRT, or Vehicle Reaction Time (rollout) is .310, because .310 and .190 = .500
You'll also develop the ability to "know" when you are late or early, and will have a good base upon which to adjust your car to your needs, for instance you'll know that 5 lbs. of air in the fronts is in fact worth .010, or whatever it may be, to your track reaction times.
I have a Port-A-Tree Eliminator 2000 practice tree, and a Biondo Mega-Box in my car to compare my DRT's between the practice button and the one on my wheel.
Also you'll become aware that there are those days when you just might be .020 better or worse on the tree, and that is the way it's gonna be that day, you roll with it and adjust your car, always hitting that bottom bulb the same, like a machine.
Now when you want to have some fun with the practice tree, set it on "random dial in" mode, and hit BOTH bottom bulbs with both buttons.....when you can focus in and do that, you'll kill at the starting line on the track.
NOTHING will be able to rattle you on the line.
It's "bad practice" to just want to set the practice tree to where you get good reactions and sit for hours upon end...your eyes get funny from "photo-flash".....use the button for hours to get a repeatable motion of release, but once you are grooved in, turn on the tree, hit it no more than 4 or 5 times, with a break in between, in other words, "practice like you race" mentally.....I like ot leave mine on, and might walk by it once or twice in a day, just pick up the button, hit it, and walk away......wait a while, come back and do it again.
When you can put it away for several days, fire it up and hit your number, and walk away, you've kinda mastered it.
Oh yeah, "in car" testing has also shown me that your "in the staging lanes with the engine running" DRT might be as much as .020 quicker than your "at rest" practice DRT, just because of the adreleline of being strapped in and ready to race....just keep all that in mind when setting your VRT and making your adjustments.
Basically, the more "mindless" you can make your starting line and run routines, the better racer you will be.
I could in no way begin to describe anything that goes on inside my car after the burnout, I'd need film to be accurate about how the shifter works or anything....All I know when I'm "on", the shift light just barely blinks on both gear changes, and I see a lot of win lamps in my lane.
That's the best I got for ya. 8)