You type dimensions for rectangle in wrong format:
when you type "2000,2000" AutoCAD takes this as absolute coordinates and puts the opposite corner of the rectangle at coordinates x = 2000 y = 2000 of current coordinate system.
You should use in this case relative coordinate input and type @Anonymous,2000 when AutoCAD asks for other corner.
Not sure about offset - it should work correctly.
Can you attach drawing with wrong offset results?