Photoshop changes measurements and proportions of canvas for no reason.

[sven2911]

I designed a Flyer for Print. Measurements should be 5,5 cm x 8,5 cm. After printing I discover that nothing fits, and after checking the canvas size its 10,3 cm x 20,4 cm. Resolution was 300ppi.

How do I prevent this?

[JJMack]

Photoshop does not do anything on its own... On its own is sits there waintng on you to use it.   So please tell us how you used it. What exactly did you do.