To make a rectangle using coordinates, you need to deactivate the Dynamic Input option from the status bar. To turn it off, click on its icon in the status bar or press the F12 function key:

When Dynamic Input is on, a tooltip will show next to your cursor and when it is off, you won’t see a tooltip, as in the following screenshot:

Here, I will make a rectangle that starts from the origin and has a length of 8 units and a width of 3 units:

The following is the workflow for making this 8 x 3 rectangle:

1. Click on the Rectangle tool in the Draw panel or type the REC command and press Enter.
2. The command line will prompt you to specify the first point. Type 0,0 and press Enter.
3. Then, type 8,3 with the next prompt and press Enter again.
4. The final rectangle will be made with a length of 8 units and a width of 3 units.

In this case, the first point was the lower-left point of the rectangle, shown as 1 in the following diagram, which is also the origin, and the second point was the upper-right vertex with coordinates 8,3, shown as 2 in the diagram:

For point 2, we added 8,3, where 8 is the length as well as the X coordinate value and 3 is the height of the rectangle as well as the Y coordinate.