We have a "round box" object. The dimensions along the x and y axes are the same. The page is in "rotated by 90°" mode. I move this circle to a corner so that it partially extends beyond the dimensions of the page. Then we scale it while holding down the shift key. At the same time, smart guides are turned on. The edges of the circle begin to deform, trying to stick to some reference line. As a result, the dimensions of the circle along the axes become unequal. The difference is only after the decimal point, but it is there.