Click on your actor and under the "Attributes" select "Graphics" (open up the down arrow) and where it says "Horizontal Wrap" and "Vertical Wrap" set them both to "Fixed".
You do want to make sure your graphics are at 72 pixels per inch, but don't worry about the odd pixel dimension if you set the wrap.
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You do want to make sure your graphics are at 72 pixels per inch, but don't worry about the odd pixel dimension if you set the wrap.