When you add a new section, by default it has a Minimum Height of 500px. If you add a container to this section, that is 280px height, the whole section is still going to be 500px because the parent section is set to that.
If you set the Minimum height of the section to None in the Inspector Panel, then that section will wrap to the size of the container that you added earlier. I think you will find it easier using the Inspector Panel to set your sizes and heights rather than dragging.
You can learn more here - https://www.editorx.com/academy/video-tutorials/inspector-panel