Hello everyone!

I am trying to create a chart. Here is what I am trying to do.. I need four columns. A,B,C then the fourth would be ABC combined togther (this one I need it to be stacked) I have looked around online. And I know I need to enter a couple of "blank" rows. However I cannot separate them now. I have my stacked column above A,B,C. I've tried changing the Gap with but cannot get it to separate. Any suggestions on what I am doing wrong?

Any help is greatly appreciated!