Bug Screen resolution Bug on editor

Im making some code for UI animations and i need the screen width to make it work ricght. The code its this little thing:

var scaleX = Screen.width / m.width;

var scaleY = Screen.height / m.height;

It works allright the first time i invoke the method, but the first time its bugged and the screen width value its changed even if i dont touch the game window resolution.

As you can see in the image, the screen value (Screen.width) has changed, bug im playing on fixed resolution 1920x1080

The bug only happens on editor, it works well on builds, but i want to reset my animations for testing on the editor instead of having to reset the game. Its this a bug or can i solve this with something?