Bad Brad
Brad, a poker player who isn't known for his skill, gets Harlan to fold a hand that would have won him a large pot. Harlan sees one of Brad's cards and realizes he was bluffing. The card is a symbol to Harlan that he is playing with amateurs, not pros which causes him to to go off the rails from here on out.
Spreadsheet
Dean snaps at Molly, asking her if she's keeping track of the buy-ins. She tells him yes, but he wants to know where the sheet is. She points to a spreadsheet on her computer. And this is a symbol that Molly is far smarter than what Dean's expectations point toward.
Bad Bet
Harlan was beaten earlier in the night by a bad bet from a player. So when the same move comes up from a player while he's trying to scrap together a win, he won't let it fly. He goes all in. But the player wins on the turn and the river. This is a symbol of Harlan's going off the rails and playing off impulse and revenge rather than skill.
Back to Even
Harlan is strung out on redbull and booze when he asks Molly for $500,000 to get back to even. His ask is a symbol of his never ending desperation to win his money back. Something he doesn't do, but instead presses himself further into oblivion when he loses it all.
Hot Chocolate
Molly's dad offers her a drink and she snaps at him that she can't because she's an alcoholic. He tells her it's hot chocolate, and he points out that her believing the drink was alcohol points to the symbol that she doesn't even know where she is. She is on a park bench near a skating rink, not in a bar.