Basic Strategy Deviations Chart Need Help Understanding

I was reading and came across this chart and I am having a difficult time comprehending what it is telling me to do. The chart title says 20 most important variations by number of decks and looks a little something like this.

Hand | 2 Decks | Quick Key
12 v 6 | -8 | (I) (I) = Initial Count
12 v 5 | -8 | (I) (D)= # of decks
12 v 4 | -2 | (-D)
12 v 3 | 0 | 0
12 v 2 | 2 | D


this is just a bit of the listed deviations that it says to remember. What i believe it is saying is that when you have 12 v 6 you hit if the count is -8, but I have no clue if that is right. I am trying to learn the basic strategy deviations and came across this but i have no idea what a quick key is either. Any help would be great, thank you.

I've never heard of a quick key. I'd ignore that information.

Google "Hilo illustrious 18 index". Or buy a book that has them. Or get CVCX/CVBJ. Index values are in there.

thank you

There's also https://wizardofodds.com/games/blackjack/card-counting/high-low/ .

Personally I go by gut feeling for some of the close plays - but then most my games are now CSM.