Calculate to values

1

Hello,

how can I pull out these two values and calculate them?
I would like to calculate end - beginning = sum and output this.
Thanks.

    Anfang = from(bucket: "VH_Messwerte")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["topic"] == "Energie/VH/Zaehlerstand/aktuell")
  |> aggregateWindow(every: v.windowPeriod, fn: last, createEmpty: false)
  |> first()


Ende = from(bucket: "VH_Messwerte")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["topic"] == "Energie/VH/Zaehlerstand/aktuell")
  |> aggregateWindow(every: v.windowPeriod, fn: last, createEmpty: false)
  |> last()