problems while creating a loop

I tried to create a loop to enter some givenname/surname pairs. I therefore worked as described at the documentation (http://customfieldsuite.com/field-types/loop.html)

To use it, first create a Loop field. After saving, drag other fields directly below the Loop field. You will notice that the fields will appear “nested”.

But I don’t get the two textfields nested. There is an empty row and after the rows exactly one textfield for givenname and one for surname.

I’m not sure how to get the loop working, because all dragging tries of me didn’t work.

Any help is welcome, Stefan