Substract a value x from a prometheus metric for a grafana "single stat" with "Delta" activated?

Maybe the problem should be solved in another way...

I am using a grafana SingleStat pane with "Delta" activated and the dashboard shows me "today so far".

prometheus metric: sum(request_duration_count{...})

Problem:

• I have a metric counting requests. Between 03:00 and 06:00 an automated test triggers my service and the metric is incremented by value x. (I set a grafana annotation at the starting point.)
• I want to get a single stat request count without the test requests.

Advanced Problem:

• Nagios checks every y minutes and also increments the counter.
• How can I remove these "test-counts"?

Any ideas :-) ? THX in advance!