Security: registration (with personal data) in a public store. Using the price scanner: 7 seconds without any action, should it be interrupted?

Sketch

Download bmml font – Wireframes created with Balsamiq Mockups

I am creating a registration process for a loyalty program that will be taken in the public space (store) – Kiosk alike. Users will enter their personal data such as: phone number, name, email, so if someone decides to leave it in the middle of the process, the data should disappear (for security reasons) and the welcome screen will be displayed> I tried to show screen in the middle of the process with the countdown of time: 7 seconds

What do you think, how long should the automatic interruption take when there is no user interaction? Also, I added a kind of "panic button" that can be a user if the user wants to interrupt on request.

The users are very diverse: from 14 to 80 years of age … so it should not cause much stress and, on the other hand, I can not leave too much time for anyone to see the data of previous users …

My main concern is that when a user searches for his email number r on his smartphone (for example) 7 seconds will remain safe and everything will disappear … So, how much time should I give users to complete this step?