IP addresses vary in scale in terms of the number of devices behind them. There are many, many reasons for this including corporate gateways, mobile networks, C

IP addresses vary in scale in terms of the number of devices behind them. There are many, many reasons for this including corporate gateways, mobile networks, CGNAT, VPNs, public wifi and yes, even home NATs. There's no "normal" UA cardinality count that you can use for filtering. However, there may be other traffic characteristics that are useful; the shape of the distribution, for instance.