Values get rounded during task

Hello, how can i prevent rounding values in influx.
I have two Values in a double type field.

179,5 HM800 yieldtotal from 30.6. 0:00:0
and
180,1 HM800 yieldtotal from 1.7. 15:00:0

after difference() and sum() i get 0,5 and NOT 0,6.

Whats going wrong here ?

This is my query :

import “experimental/date/boundaries”
import “timezone”

option location = timezone.location(name: “Europe/Berlin”)

month = boundaries.month()

from(bucket: “PV”)
|> range(start: month.start, stop: month.stop)
|> filter(
fn: (r) =>
r[“entity_id”] == “HM800_yieldtotal” )
|> filter(fn: (r) => r[“_field”] == “value”)
|> difference()
|> aggregateWindow(every: 1mo, fn: sum, timeSrc: “_start”)