Count the number of selected check box in a matrix field

Hi, I have a matrix "operatori" and i want know the number of selected check box.

In the image there are the different steps that i did. I want have in calculation example B the number two, but I don't know the problem. Thank you for help

Hi,

You don't need to use count function. That is only applicable for checkbox fields, not matrix fields.

Removing the count should fix it.

Example:

Thank you