In order to calculate damage done, you need to input the number of icons done. From there, you have to select your strength range from the drop-down list; a higher strength boost yields more damage. In addition to that, you can also select stances for both you and your opponent from the available selections. Stances apply a multiplier to the damage done. Cautious, the default, has a multiplier of 1. Once you've done that, click "Calculate" and see how much damage is done.