Artboards not the size they say they are?

[dijonaise]

I set up a document with an Artboard at 75mm x 340mm. When I draw a rectangle (snapping to the artboard) it comes out to 70.194mm x 340.194mm. Why is Illustrator unable to do the most important basic thing - being accurate. My work depends on accuracy and once upon a time Illustrator delivered. How can I turn this over to vendors knowing I can't guarantee the most basic thing - size?

Look at the screen shots: The Artboard is a different size! Which is correct the drawing or the artboard - who knows! Centainly not Adobe

Artboard at 75mm x 340mmRectangle at 75mm x 340mmRectangle at size of artboard - 75.194 x 340.194mm!

[Ton Frederiks]

Is Preferences > Use Preview Bounds checked?