I've always learned that you stand 2-8 and double-down on 3-6, hit 9+. And if you CAN'T double-down, then you stand on 3-6 (http://www.blackjackinfo.com/bjbse.php) Anytime I've opted to STAND on a soft 18 that I can't double-down on, such as when I've already hit once, I get marked incorrect.
The chart on this site, which the game is following, just says double-down on 3-6 (and ostensibly HIT, if you can't double). What's the correct play in real life, are these other charts incorrect?
I learned "A,7_6DOUBLE-STAND/STAND All Else" (or "A,7_6D/S.A.E." if you prefer. So, i DOUBLE a soft 18 to dealer's up-card of 6 (and STAND if i can't double) and STAND on all other dealer up-cards. http://www.blackjackapprenticeship.com/resources/charts/