Sizing problem whit machin and picture

The working size of my machine is 500mm500mm.
first problem.
I would like to burn a 200mm
200mm image, but in the lightburn program I have to change the size to 450mm*450mm so that it corresponds to the size of the piece of work during the burning process.
second problem.
When moving the machine, the step on the machine is also longer than the default 10mm step, which is 25mm based on measurements, but in the program, the removed step is only 10mm, and this happens on the ax axis and the y axis.
Does anyone have any ideas or help to solve this?

seems to me you have step per mm settings incorrect on your machine

usually for nema 17 the steps per mm are roughly 80-100, you need to very really with your controller/Stepper combo

My setting is 80 steps/millimeter