When you start the marathon, unless you plan to go sub-three, it doesn’t matter much where you’re standing.
Sure, you probably don’t want to be stuck in the line for the restroom when the gun goes (it happens), but generally speaking, over a 42.2km race, the first 500m won’t matter much.
With the marathon, as with all bigger events or projects, the important thing isn’t “where” you are at the start, the important thing is that you start.