How do i make this return the value i want?

So, been making a lot of posts recently due to me making a damage indicator script without any guides (just so i can challenge myself) anyways, i have a value that should print out how much dmg the player took but it doesnt seem to work as i intended it to be, for ex: CurrentHealth = 100, newCurrentHp = 90 if i minus those two, its 10… Well, if i switch newCurrentHp to 80 it will print out 20 not 10 bcuz the CurrentHealth is 100 how do i make it so when a player dmgs a player it gets them to 90 hp it says 10 but when they get hit AGAIN it also says 10? also here is the script:

local NewCurrentHealth = damageTaken2 - CurrentHealth
local newCurrentHP = math.abs(NewCurrentHealth)
local damageTaken = newCurrentHP - CurrentHealth
print(damageTaken) --Prints 10 but when i hit them again its 10 again

Edit: i tried using health aka which was 90 and 90-90 is 0 so didnt go well

Edit2: i tried another variable which was newHp and its value was 10 and 90-10 = 80 which again, didnt go well since the dmg that was done isnt 20

Nvm i just found the answer…
Just had to use math.abs