Can you adjust the size of the pop-up dialog box in Rules

I'm using HTML in the pop-up dialog box under Action: Display a message in rules. I'm trying to figure out how to change the size of the pop-up box because the amount of text I have is difficult to read when I start using lists. It needs to be wider. Is it possible to set the size of the box somewhere?

I tried adding an image that would be as wide as I want the box, but it just creates a scroll bar at the bottom.

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Candace R.
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