You may have started buying a stock at $24 dollars. You buy 10 shares. The new price of the stock might be $25. Now if you were to sell this stock again, it would just return back to $24. In this case, your are "up $0.00".

That's why in some cases even if the price of a stock is currently greater than where it was when you made a purchase, by the time you actually sell the whole position, the price could end up being lower.

In this example, the price was $25 when you were done buying your position. A few days later the stock goes back down to $24.50. This might be greater than $24, but when you sell your 10 shares, the new stock price might dip to $23.50. This is now less than what you originally started purchasing it at, and you will incur a small loss. You'll see this field as a red "down $0.50".

Note: Your position may actually be worth a whole lot more (or less) when the stock closes out and pays its shareholders back on whether or not the prediction came true.