According to Nielsen, Dahmer debuted with over 3.7 billion minutes streamed in the timeframe between September 19 and 25, making it the #1 piece of streaming content in that window but also "the tenth most-streamed program in a single week ever recorded" by the tracker. The new series, starring Evan Peters as the titular serial killer, has been a hute hit on the streamer. According to Netflix's own metrics, Dahmer has been watched over 824 million hours in its first 25 days of release with. At this point only Stranger Things season 4 has been watched more than Dahmer.
What's worth noting about Dahmer is that its viewership only went up in weeks two and three according to Netflix. So if hte series has already entered the Top 10 single weeks ever for Nielsen, it's next two weeks will almost surely make the list as well. You can find the most recent Streaming Top 10 (for the week of 9/19 to 9/25) according to Nielsen below.
#10 - Stranger Things - 416 million minutes streamed