How returning customers are counted
By the phone, not the person. A gap of three hours starts a new visit.
The box recognises a phone it has seen before, which is how you can tell a regular from a first-timer without anyone filling in a form twice.
A device seen again after more than three hours counts as a new visit. Somebody who stays all afternoon is one visit; somebody who comes back the next day is two.
Modern phones scramble their network identifier for privacy, but they use the same scrambled one for the same network every time, so returning customers still match correctly.
Two caveats worth knowing: someone who forgets the network and rejoins may appear as a new device, and a person with a phone and a tablet counts as two.
More in your customer list
If this did not solve it
Email hello@margovy.com. Tell us the venue name and what you were doing when it went wrong, and a person will reply.