Using Scanner ID is a feature that's used to differentiate functionality for Scanner Apps, so that they can have different rules and actions. For example, you could setup a specific Scanner ID so that every time a card is scanned a stamp or a certain number of points is added automatically without needing any further user interaction. You can also use Scanner ID to be able to know where a wallet pass has been scanned. Don't hesitate to contact us if you have questions and we'd be happy to guide you.
If you accidentally choose the wrong Scanner ID, refresh the page and you will be able to choose again.
Related
How to use the Scanner App
How to scan, verify and perform actions.