Your Installation Manager window looks to be the same ratio of window to screen as mine roughly, so do you have your system set to a low resolution or perhaps have your fonts set to a larger size than standard?
Try holding down Control key and "-" to zoom out when you have the mouse focus on the Installation Manager. The Installation Manager uses webpage display to show the pages and they will follow the same zoom in/out shortcut that browsers use. I am thinking that you changed the zoom scale somehow based on the image you provided.
Based on the size of the icons, it could also be that your display scaling is zoomed in. If you right click on the desktop > display, then there should be a link in there to adjust the scaling.
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