"Days" operator in Aggregate indicators - not working?


I am trying to use the “Days” operator in an aggregate indicator, in DHIS2 v2.26. I cannot find any example in the play demo (v2.27). In the user manual (for 2.26) I find the following:

(and I note that the example has an error, it should be (30-25/30)*100 = 17%)

From this I had assumed that I could make an indicator in a weekly dataset where the indicator is

Indicator type = 1 factor

Numerator = [days]

(selected from the window – as below)

Denominator = 1

Expected result = 7

Actual result = 0

Please can I have some advice on what I am doing wrong? Or is the operator not behaving in the expression as expected?

Thank you