Question about trendstl function

[machinelearningdingetjes]

Hi,

I have the following trendline from my dummy data:

As you can see, it is 100% seasonal. But still I get the following result when I use the trendstl function with the following parameters:
Result: 1>0
Parameters:

trendstl(<key>,4w:now/w,3w,1w)>0

Can anyone explain this to me? It should give back 0 anomalies because all the data is seasonal.

Greetings,
machinelearningdingetjes