How to customize Checkboxes in advanced designer?

Choosing a round style, how can it still be square? Where do I need to set the operation? What should I do?

I tried locating the form with the fields as displayed in your illustration above and I could not find the form I have however cloned on of your form and used it for the illustration below:

You will need to save the configuration made on advance editor for the changes to be effected. Below is how I did on the cloned form.