How would I make damage and health work in a rpg like way? [closed]

Hi! Some time before I posted this. And when I posted that, I learned I was using modules WRONG and didn't understand them right. And in the tables I put in the module script, I put damage and health as some stats of the pets in this case Ducks. How would I go about doing the health and damage system?

How it works:

You click on the other duck, so you target / lock on to it. Then you chose one of the abilities on the bottom gui. You have to be a certain level to use certain abilities. When you attack them the targeted / locked on Duck's shield / health goes down to according to the damage of the Duck, and the multiplier of the damage on the ability / attack.

Thank you for your time!

Duck -Damage = 1- -Health = 2- (Use this as an example please.)