But if I were to do that (with sample made up numbers): Android - 700 users worldwide Functionality - 500 people in the demographic That certainly doesn't me

But if I were to do that (with sample made up numbers): Android - 700 users worldwide Functionality - 500 people in the demographic That certainly doesn't mean that there are 1200 potential users, as I don't know where the crossover between people who require the functionality and also own an Android device are. In a technically disinclined demographic, maybe only 50 of the users that require the functionality also own an Android device - and only 10 of those would be willing to pay for the (an) app.