The Bankroll chart shows your total profit based on your current filter settings.
The X-axis is chronological order: older hands or tournaments are shown first.
Tournaments: The X-axis is the number of tournaments played.
Ring Games: The X-axis is the number of hands played.
Showdown Winnings (Ring Games only): Use the Showdown Winnings checkbox to add two new lines to the chart. These two lines split your total winnings into showdown winnings and non-showdown winnings. If you add the Showdown Winnings line to the Non-showdown Winnings line, the result is your Total Winnings line.
Trendline: Use the Trendline checkbox to add a trendline for your total winnings. The trendline is a best fit straight line showing the direction your winnings line is trending. A linear regression calculation is used to generate this line.