anybody knows what does dell power manager under battery settings: "primarily AC use" specifically what it does ?

does it limit battery charge to 96% instead of 100% ?

i am on battery setting "Primarily AC use" and when my dell xps 13 is plugged in, it still charge battery to 100%. Is this normal ?

I am plugged in most of the time at least 8 hours a day. which battery settings would be most recommended ?