Incorrect network usage/bandwitdh usage ?

Greetings -

We have an IPsec s2s over which SAN replication takes place.
ASG 8.305 virtual (vsphere 5.0 U1, VMXNET3 adapters) at our end; another ASG at the other end (don't know what version).

On our side, while watching the Network Usage/Bandwidth Usage under the Logging and Reporting section we cannot see the accurate bw usage.

For example, the local SAN's IP address has received 4 TB of data so far (after some days); Astaro's Network Usage/Bandwidth Usage only shows 2 GB.

The SAN is constantly pulling 40-60 Mbps; per last days we only see in reports a couple of MB to/from SAN's IP address.
Furthermore the daily firewall reports do no take into consideration the SAN traffic.

Interestingly, the Flow Traffic Monitor functions properly; it reports the 4TB and it shows the almost 900 GB of traffic for a current established data replication connection along with the correct connection speed.
Also, under Network Usage/Monthly it is correctly displayed the bw usage (Mbps) since the replication started; we see a constant line for the 40-60 Mbps rate.

Any clues what's wrong with the Network Usage/Bandwidth Usage and daily firewall reports ?

Thank you,
Adrian