BEx InfoCube calculated key figure based on a formula variable

Hi all, I'm facing a problem with BEx calculated key figure, the ones that can be edited starting from the left pane of Query Designer.

Precisely, I need to sum the values coming from a series of attributes of a single characteristic and then restrict the result using a time characteristic. To do so, I created a series of formula variables that point to the InfoObject's attributes and then a calculated key figure at InfoCube level (left pane of Query Designer, as said before) that sums them. Finally, I positioned this key figure among columns without doing any restriction.

The problem is that it shows always 0, even if InfoObject master data are correctly loaded.

Furthermore, the same calculation made through a formula (right pane hence), shows the desired values; unfortunately, it cannot be restricted and, as a consequence, I cannot reach the result I want.

Which could be the reason? Why the calculation differs, even if it is defined exactly the same way?

Thanks.