I see. In that case, I view this as a cost benefit trade off. How valuable do you think mentioning this extra "bonus" will be to your application? If you think it is highly valuable, then tack on a sentence or two explaining it in your optional essay. Personally, I don't think the adcom is going to put a lot of weight on it, so I would just lump it in with the bonus and be done with it. That one or two sentences could be used for something else (I know that your profile is somewhat complicated already, so why complicate it more?) or left out entirely. If you start adding extra details to your app that are of marginal value, I think you risk annoying the adcom.
I'm not trying to down play your accomplishment (nice job), but I think you should consider this piece of info. in the totality of your app. Is it going to be a difference maker in your candidacy? Given that you are high up the ladder already, I would say probably not.