Bandwidth Monitoring of all the interfaces will happen at a pre-defined interval of 5 minutes. The In and Out bandwidth utilization values in the summary view will appear in the next polling cycle, i.e., after 5 minutes, which will be the cumulative bandwidth utilization value in the past 5 minutes.
If problem persist try changing the SNMP version as explained here.
The speed of the interface shown in the Bandwidth Monitor tool is retrieved through SNMP from the device. If this is not properly configured, you might see an incorrect value and subsequently incorrect utilization percentages as it is calculated based on the speed of the interface.
To change the Speed manually, connect to http://localhost:7080/network/ifSpeedChange.jsp, change the value and Save.
The SNMP version of the device is automatically detected by OpUtils based on the initial responses from the device. You need not change the version while adding the interfaces.
But, in some devices, there could be cases where the subsequent queries to the device will not get the required results. In such cases, the bandwidth utilization of the interfaces will not be shown even after two polling cycles (10 minutes). If you face this problem, delete all the interfaces and add them again by selecting a different SNMP version (if v1 is auto-detected, select v2c and add)