Half of it. This gives you the running count. You need to also keep track of “number of decks in shoe” -“number of cards dealt since last shuffle”/52 to tell you how many decks are left in the shoe, then divide the running count by the number of decks left to give you a true count.

True count higher than 1? Start increasing your bet accordingly.

Those rules are probably set by advertisers, not be reddit themselves.