Post Function Process View size

My plugin has a Post Function and when that Post Functions view is displayed it is a lot larger than is necessary for the information displayed

The view is just an HTML page with the html and body tags and the text is displayed in a div. The only css is on the body tag (style=“background-color:transparent;margin:0 !important”)

The iframe displaying the view has a height set to 150px.

How do I stop this view being so large?