Calculating the bits/sec from traffic counter values

I’m using the following query to get bits/sec from the counter values for ifHCInOctets:

SELECT NON_NEGATIVE_DERIVATIVE(MAX(value), 1s)*8 FROM ABC WHERE hostname=‘myrouter’ AND metric=‘Gi0/0_ifHCInOctets’ AND time >= ‘2017-11-01T00:00:00Z’ AND time <= ‘2017-11-30T23:59:59Z’ GROUP BY time(1h) fill(previous)

The issue is the values returned by the query above don’t seem to match at all with the values I’m getting for the same device & interface from Graphite.

I’ve also tried replacing MAX in the query above with FIRST/LAST/MEAN but the valued returned are still quite different from what Graphite gives me.

Is there something wrong with my query?
Would appreciate any help/pointers.