[2022] Shock effect rounding question

As a new player I have a question about rounding when it comes to shock - shock removes 5% of lightning resistance per stack. If I have 20% increased effect, then this number goes to 6 and is easy to calculate.

However, if I only have 15% or have 25%, how would it work in this case? will it round up the 15% increase to also increase each stack to 6%? Does it use decimals?

Also, personal pet peeve I guess - why does ailment bar under monster shows 15+ shocks when you can go to 20, wouldn't it make more sense to have it not show above 20? Sorry about this small rant.

On the positive note, I did play LE before a bit but coming back to it after about a year shows great deal of progress, especially endgame and crafting is sooo much better now, looking forward to sinking couple hundred hours into it.