Merge queries in grafana


I am working with the integration of Grafana with zabbix to implement a graph of the rate of an interface of a Cisco Router.

Receving the values in Octetos in Interface, i aply the scale (8) to put the value in bit and apply the rate to have the delta value.

Now i am trying to merge the values but i can not have the correct graph. In other modes it works perfectly (stat for example)

Someone can help me? Thanks