bandwidthd question

[the_2PC]

I have 2 interfaces, LAN1 and LAN2. If i wanted to all traffic going though my pfsense box would I select wan as the bandwidthd interface? If Im understanding correctly, whatever interface you chose is where it will measure. But when I selected WAN it never populated a graph.
When I select LAN1 and the bandwidthd interface, it then populates data. Im still not completely sure what the subnets for stats collection does. If LAN1 and LAN2 are 192.168.1.1 and 192.168.2.1 respectively, would selecting both of them under stats collection actually monitor usage over both interfaces? if so, im totally lost on how and why. Or is it only going to measure data moving across lan1 and 2, but not measure traffic from lan2 to wan?
Is there a way I can set it up to measure the bandwidth of both?

[the_2PC]

bump?