How to adjust the position of clones in a matrix?

How can I define the position of clones (buttons) in a matrix ?

I have created a button and cloned it x time in a matrix.
x is defined by an input. When x=5, the matrix only shows the 5th buttons, which is what i want.

But I would like to layer all the buttons, to have them at the same place, and don't have the impression that the button is moving when x get a new value.

All the buttons are shown when x=0, but I wouldn't use this value.