Unique period in graph

[Bart_Breekveldt]

Dear community,

I've set up a custom time period (4 weeks). Our company works with periods instead of months. My script is as follows:

=Dual('P'&Num((Week([Order.Leverdatum])+1)/4,00),Num((Week([Order.Leverdatum])+1)/4,00))

(Order.leverdatum (Dutch) translates to order.delivery_date)

However in a graph it looks like this (see below). When selecting "period" I get the same graph as when I select week. The period shows up four times and are aggregated as weeks.

I've tried GROUP BY, AGGR and DISTINCT funtions, but it didn't help. What am I doing wrong?

How can I aggregate these period, so my graph show the orders per period?

Thanks in advance