I assume that we have 4 assassins to match our 11 players.
If we lynch one per day, that puts us at (worst case scenario):
day 1 4 - 7 > 4 - 6 > day 2 4 - 5 > 4 - 4 and loss during the night
So we get one mislynch.
If we double kill today,
4 - 7 > 4 - 5 > 4 - 4
So we need to kill one person today but not two people and we've got a single mislynch.