Logql query avg and sum gives same result

Question

I have a logql query for loki on nginx like this:

sum(avg_over_time({$label_name=~"$label_value", job=~"$job", instance=~"$instance"} | json | status=200 | unwrap status | __error__="" [$__interval])) by (upstream)

this gives me the result same as

avg(avg_over_time({$label_name=~"$label_value", job=~"$job", instance=~"$instance"} | json | status=200 | unwrap status | __error__="" [$__interval])) by (upstream)

It means sum and avg result are the same and both gives me the sum of values. What is wrong with my query?