Como posso definir apos quantas submissoes o e-mail de notificacao devera ser enviado?

I am not exactly sure what are you trying to achieve. 

If you set up the Email Notification inside of your form, you will receive it each time your form is submitted. If you have only one email Notification, only one email will be sent, unless you have some conditions set inside of the form for the email Notification. 

Do you maybe want to limit the number of submissions? If so, please check this guide:

How to Limit Submissions in a Form

If I did not understand your question correctly, please explain in more details what are you trying to achieve and provide us an ID of the form you are working on.