What 2 interfaces to monitor

Hi, I have a Cisco 877 ADSL router. It is based in a remote office setup in VPN mode to my HQ. I am using the free version of Netflow (2 interfaces) on an Windows XP PC at the remote site. What interfaced should I monitor? I ham VLAN 1, Dialer 1 and ATM 0?

At first I monitored VLAN 1 and dialer 1 and I copied a 500mb from the HQ to the remote site, it finished after 10 mins, so I looked at Netflow over that period on both interfaces and it only said that PC 1 at the HQ copied 10mb to PC 2 at the remote site. I thought maybe the routers time was wrong but it wasn't. I tried the last hour view at it said 10mb only, why not 500mb?

Thanks