How to align buttons in ae scripting withing panels and groups?

Hi there,

My name is Bram Hoekstra.

This question has probably been asked to many times, but I can't find the correct awnser for my case. I'm building a script to easily create movie credits, but the aligment of the buttons in the scriptui panel, doesn't appear to work. I've provided an example of the way the buttons should be aligned. The containing rectangles are the groups where the buttons are in.

How can I code it so, that the buttons appear as in the example.

Thanks in advance for your help.