When cooking scallions it takes about 10 minutes to cook the scallions.
You cook the scallions about 5 minutes each side and 10 minutes is usually enough time to fully cook the scallions.
If you cook the scallions longer than 10 minutes then you could overcook them and ruin them so make sure you watch them while cooking them.
Set a time for 5 minutes and allow the scallions to cook on one side and then when the 5 minutes is up you can then turn the scallions over and allow the scallions to cook another 5 minutes on the other side.
The scallions cook pretty fast so you should watch them closely when cooking them.