FortiGate Network bandwidth

Hi teams,

Hope you are doing well today.
I am new to Grafana, i wan to graph my FortiGate interface bandwidth.
So i have created to metrics FGifOutOctets & FGifInOctets. Sio both metrics are counter32 value.

When i graph this two metrics in Grafana, i have straight line at 4Gbps for both, but nothing regarding current bandwidth …(my ISP provide me a 100Mb line).

How can i make some filter in order to graph my current bandwitdh ?

Many thanks