This retirement monte carlo simulation based on past data from the Standard and Poor historical averages (Average Stocks Return), the 10 Year Treasury Bond (Average Bonds Return), 3 month T-Bill (Average Cash Return), and US inflation. For each year of each simulation event, a random return and inflation amount is chosen.
The percentage on the right shows the percent of simulations that did not run out of money before your life expectancy (80). For example, a 90% probability of success means that only 10% of the simulations did you actually run out of money before the age of 80. You want to be above 80% probability; above 90% is ideal.
The chart below will give you this percentage throughout your entire retirement.