What does it mean, 'pax'? No - it's not 'peace', in this technological context. Pax here does mean: "persons approximately".
It's some sort of 'industry jargon'. You better should say: "people counter".
Depending on available WiFi and BLE signals around, it could be, based on statisticsl methods, calculated, how may people are gathering in a crowd nearby the detection device. Not the individual MACs are stored, but the sums of those, being all together and also their changings over time - all live repeated in minutes!
Note: It's not about individual tracking!
This could be helpful, generally spoken, in all places, where people are gathering, as a more or less, big crowd and it could be useful (e.g. for public services, shopping malls, public transport companies, etc.) to know (approximately) how much people there are together.
You may find the code there, if you like.
Pls, regard your national laws, regulations and restrictions, if applying.