Your demo apps have an install limit of 10 installs. You can see the number of installs on your dashboard, under your app's title. The number before the slash is the current number of installs, and the number after the slash is the maximum number of installs allowed.
If a new user tries to install a demo app that has reached it's install limit, they will get an error message such as the one shown below.
7If a user uninstalls the app from Yapp, the count will be decreased by one.