So I understand the concept of standard deviation being proportional to the square root of variance, but when you’re playing blackjack, you might go 5 shoes and never see a TC over +1, or you might go two shoes and both of them hit TC of >+5. So what do you pick for your session bankroll?

I used to assume a normal distribution, and 3 standard deviations, and I was quite smug in my mathematical certainty. Now I just take my max bet (for two hands) and multiply by 20. And I leave 3 bets in reserve in case I split, then split, then double.

What do you do?