I also recall when I worked on a European-designed typesetting machine, the language had me specify the vertical dimension first, followed by the horizontal dimension. So when I would created a 9 1/2 inch x 11 inch continuous form design (that ran on a web press with perfs at every 11 inches), I had to key the size as 11 x 9 1/2.

So my next question would be, when you specify 5x4...

Are you doing it because you are specifying the long dimension first?

Or are you specifying the height first?