That looks like you have a style setting the width to 100%.
To confirm this, in your browser, inspect the element. You will probably find a style with width: 100%. This is the style you will need to change. I expect it will be in a custom theme, so you will need to find where else this is used and make the selector more specific.
Good luck!
The tooltip's default CSS styling is likely preventing it from expanding or wrapping its content. This is commonly caused by:
To fix this, you'll need to override the default Mendix/Atlas UI CSS for tooltips.
Thanks, hope it helps.