The image is just a simple chart without any real numbers attached, so there's no telling just how popular that emoji is over all the rest. Really it was just a demonstration of how Apple uses its differential privacy tools, many of which it described in the overview. In it, Apple said, "There are situations where Apple can improve the user experience by getting insight from what many of our users are doing, for example: What new words are trending and might make the most relevant suggestions? What websites have problems that could affect battery life? Which emoji are chosen most often?" But the company said getting that information while maintaining privacy is a bit tricky but key. To do that, it uses its differential privacy technology, which Apple describes as "a technique that enables Apple to learn about the user community without learning about individuals in the community. Differential privacy transforms the information shared with Apple before it ever leaves the user's device such that Apple can never reproduce the true data."
Apple says it uses these tools to improve the usability of features like QuickType and emoji suggestions, lookup hints and Safari energy draining domains, among others. You can check out the full overview here.
With the release of iOS 11.1, Apple added over 70 new emojis, and I'm betting the cursing face one will make a run for one of those top 10 spots pretty quickly just based solely on how often I plan to use it. However, iPhone X users will no longer be limited to the selection of static emojis as the company announced in September that the new phone will include the ability to animate a selection of emojis based on what you say.