You can adjust the registration limits for your program from Settings > Registration > Registration limit.
Email use limit
Select whether to allow people to register for the program multiple times using the same email, or an email address can be used only once to register for the program.
Choose between allowing Multiple registration per registration or One application per registration.
If you choose the Multiple registration per registration option you can set the maximum number of applications that can be registered per registration in the Application limit per registration field.
You can also set the maximum number of applications that can be registered in a specific category per registration by opening the category.