Anyway, the program displays a histogram of all roll results, as well as the total and other useful statistics. One thing it does not do, however, is keep a history of results, and as such you may find a simpler but less spiffy-looking solution such as the d20 Dice Bag over at Pen, Paper, & Pixel to be more useful.
The "Ace" feature was included for gaming systems such as Deadlands that have open-ended dice rolling mechanics. With this mechanic, if any dice roll the maximum value (e.g., 10 on a d10), reroll them and add the maximum value to the result. If they roll max again, repeat. So any die can achieve an arbitrarily high result, but with increasingly infinitesimal probability. I was so interested in this mechanic, I actually wrote some code and compiled my findings into an Excel spreadsheet comparing probabilities between various common Deadlands dice combinations.
Back to the Dice Roller, the ten buttons on the bottom are presets for common dice combinations. Of course, clicking one will roll those dice, but you can also right click the button to type in your own combination and override the preset.
Lastly, please bear in mind this warning from the great John Von Neumann: "Anyone who attempts to generate random numbers by deterministic means is, of course, living in a state of sin."