I originally thought maybe 15%, as I had missed the entry in the editor. I take any number that you can't verify in the editor with a grain of salt. However, the difference between 15% and 25% is so minor 1% that results showing 15% are still within the error margin for a 25% bonus.
Shabbaman, the reason for this discussion is that there are those who think the game, at least for AI units, does not follow the rules a stated. However, the combat rules are followed, hence the combat calculator can be used to estimate the odds of the battle, while keeping in mind the nature of random numbers.