By default 3D Issue Studio forces a minimum line height to ensure all text is nicely legible. This is set as 22.5%, which is also the default line height in the text editor.
If you want to reduce the line height of a Text element, you can remove this minimum. Do this by first changing the line height on the Text Toolbar. Then in the Settings section of the Properties Control Column, click “Remove Minimum Line Height” to activate the new text line height.