The most important thing to notice in an investment is that any changes that might develop in the stock could directly influence the values of the bid and ask. When a stock is trending upward, the bid will be relatively close to the actual value. When the stock falls, it bid will move down because the market expects the value of the stock to keep declining.
The Six Flags example is a good case to look at. The bid price of $59.98 might seem very low for a stock at $66.73. Six Flags might have been bearing with sizable losses recently. Sellers might have been concerned about the stock and they are not too willing to sell their stock. Selling now would result in realizing a significantly lower amount of money at this juncture.
The $67.29 total shows that sellers are willing to sell their stocks, but they want to at least make a slight profit. The stock is close to the current price because it is declining in value. The sellers will want to sell their shares to people like you on the market quickly, thus you’d have to spend a few more cents per share than what the actual existing value is.
Further research into the Six Flags stock shows that the stock is experiencing a year-to-date decline as well as an overall decline in its value from the past month. The stock is also starting to move a little more as the volume is increasing. These are factors that could have caused people to feel that Six Flags stock is starting to decline.
Of course, news stories could play a part in the process. Six Flags works in the amusement park industry. Stories about Universal and Disney offering big changes to their parks in 2018 with Six Flags not doing much might suggest that Six Flags could be in real trouble in the future. You would have to look at not only the changes with a stock but also any underlying issues that are developing with that stock in particular. The goal is to get an idea of what is happening with a stock and how it might change.