Using Blender 2.91
I had to go over the extruding section a few times , as I thought I was doing something wrong.
What I thought , I should be doing was extruding a face on the z-axis for 2m , BUT this didnt have the desired effect.
Instead I had to extrude , then set the length in the propeties. Am I missing something ??
Is default cube , which I typed [E] [Z]  thinking it would extrude the face up the z axis by 4.
Is after I went through the video again , extruding then setting the dimension in the transform properties.