Very good videos from Model Mania, especially like the shortcuts for creating keyholes, right click on mouse while hovering over a surface to reveal the bottom side of part instead of rotating view when adding mates. Now can't figure out why, using the Contour Selection Method over Traditional Method, my sketch 1 isn't good when creating the 12mm high extrusions of those 3mm offsets. I've check the net zero condition and don't see any as all arcs have tangency to the 3 circles.
but that's exactly how the instructor does it on the YouTube video.
OK... Since you've neglected to link the video...
The video dude is either:
-Adding that little sliver of the sketch to his initial extrude
-Adding that little sliver of the sketch to his second extrude
-His sketch is different and somehow doesn't have that.
Either way, you have to extrude that piece in one sketch or the other.
Look closely at 3:40 or so. Entire circle is extruded. He says "Just choose the circle itself".
Looks like daylight between the flat and your sketch, and contact in two points. This would make zero thickness geometry.