You could also refer to the object in the condition first before adding to the instance variable in order for it to reflect on THAT object's variable
For example if you put:
On object creation- Set unitname +1
That will add 1 to that object, not the ones already in the layout, just make sure it refers to the object you want in the conditions before changing the instance variable.
I'm utilizing the same for some platforms i need to change color, at first i had the same issue until i realized it needs the above, so i made a condition where if in collision with the platform it added to the instance variable. I learned that it only adds to that one object you collisioned with, not the others.