Export an image - dimensions change...why?

Had this problem forever, only the project I am currently working on, its a critical issue...

I'm currently exporting some vector art as a png file to be printed later.  (I've also exported as jpg, same issue).
And, this applies to exporting the same art from Draw or Paint.

The entire image is clearly checked to be the required pixel dimensions, and yet the saved file is always 1-2px larger (both axis).
I can draw a simple outline box, any colour outline, any thickness outline, even invisible outline...
set the pixel dimensions...and export...and the saved image will be 1-2px larger.

I have to pre-think, and reduce the border dimensions by at least 1px (both directions) for the saved image to be the correct pixel dimensions I need.

Why is this?
I remember seeing this in previous verions of Corel, and as I said, I can export as png or jpg...I can also copy the art into Paint, and then export as.
The end result is the same.