Battle damage question

Hi all , simple question , Whats the simplest way to make sure the battle damage from the enemies and the player are exactly what I want them to be, so for example.....

I have given main character 50 HP And I want the enemies to be able to deal the exact amount damage to the player without the damage output slightly changing, So I want the enemies attack to deal Minus 5HP but sometimes the Damage could be Minus 6HP or Minus 7HP , so is there a way to make sure the damage is always the same ?

On the Attack skill (skill 1), find the "Variance" field and enter 0.

Thanks very much !