AggregateWindow example: calculate gain per window (hourly daily monthly)

```
from(bucket: "Neo")
|> range(start: -1h)
|> filter(fn: (r) => r["_measurement"] == "async_m")
|> filter(fn: (r) => r["_field"] == "current")
|> filter(fn: (r) => r["location"] == "raza")
|> aggregateWindow(every: 1h, fn: sum)
|> spread()
|> yield(name: "sum")

```
calculate hourly total gain of daily and monthly and total
const data = total ,gain
hourly - data
daily - data
monthly - data
total - data

Start by clarifying the intended hourly, daily, monthly, and overall gain calculations in the provided Flux query using aggregateWindow and spread(). Then identify the appropriate documentation page for this example and define the expected output for each time window before drafting or testing the example.

Written by the indexing model from the issue text.