What does the scan number represent? If we go over the limit, does the QR Code stop working or does it stop collecting data?

The scan count represents the total scan counts of a QR code when anyone scans it.
Every plan has a scan count limit, and once the limit is reached before the month ends, your display page of QR code will be paused.
You can choose your plan to extend the limits of QR code scans. Our PRO plan comes with 150,000 scans a month and Ultima with unlimited scans a month.