How to return one value for the result of a dynamic aggregate?

[Chekov2k]

Hello,
we are using the current stable Gnocchi Grafana Datasource plugin in to query the metrics of an OpenStack cluster. At the moment, I am trying to use the dynamic aggregates query type to fill a Single Stats panel. However, the return value of the query is an array of items instead of a single value. What am I doing wrong?

The expected output of the query is the sum of the mean number of vcpus of all instances for a given search string in the given time period (I know I can do that via the resource search (aggregated measurements) but would like to apply some math to the result).

The operation I have defined is: (aggregate sum (metric vcpus mean))
and the response I can see in the Query Inspector looks like this:

...
response:Object
measures:Object
aggregated:Array[4]
0:Array[2018-03-13T13:25:00+00:00,300,16]
1:Array[2018-03-13T13:50:00+00:00,300,192]
2:Array[2018-03-13T13:55:00+00:00,300,48]
3:Array[2018-03-13T14:00:00+00:00,300,224]
references:Array[32]
0:Object
...

How do I aggregate the response array into a single value?