The location and size of controls in a parent is set with the rectangle. The xywh command sets all values for the rectangle.
4 integers define the rectangle:
x units from the left
y units from the top
w units in width (to the right)
h units in height (to the bottom)
These units are in terms of the average character size of a notional system font. The size of this system font can be obtained from the qm (query metrics) command. wd 'qm' returns the screen size in pixels, and the pixel size of the system font.
For example:
wd 'xywh 40 80 100 160'
sets the rectangle to be 40 units from the left edge of the parent; 80 units down from the top edge of the parent; 100 units wide; and 160 units high.
Since location and size are defined relative to the size of the notional system font, window definitions should display reasonably well on different screens at various resolutions.