Image decal doesn't match object despite having same dimensions

[brazenPhrasin]

I've create a scene for some packaging witgh a rectangular prism set to the dimensions the packaging is supposed to be. When I place my packaging image on the object it gets placed at 42.5% scale which is annoying, but also when I resize to 100% the image ends up much larger than the actual packaging size. it makes no sense.

to put numbers to the description: box is 831mm W by 196mm H by 146mm D. Front image is 831mm by 196mm in photoshop, when placed in Dimension and resized to 100% it is larger than the front face of the object.

[Ussnorway]

share the Dn and we can have a go at fixing it for you mate