Measure not working without variable

Hello.

Is anyone able to help me with this one? 

I have a slicer based on a calendar table's year month. Then I want to create this graph (figure below) in a tooltip where the x axis is based on the month in another table.

The measure I want to create for this graph is supposed to give me the information of the 6 months previous to the one selected in the slicer.

The measure works as in in figure below. But if I delete variable maximo and in variable result substitute it for max('Calendário'[Date]) it stops working. Do you know why?
 

Thanks in advance.